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Conference Paper/Presentations

Publication Year:  2016
+ Continuous Switching of Ultra-High Voltage Silicon Carbide MOSFETs
  Bilbao, A. V.; Schrock, J. A.; Kelley, M. D.; Hirsch, E.; Ray, W. B.; Bayne, S. B.; Giesselmann, M. G, "Continuous Switching of Ultra-High Voltage Silicon Carbide MOSFETs," IEEE International Power Modulator and High Voltage Conference (IPMHVC), accepted for publication, 5-6 July 2016.
Abstract:  Not Available
+ Evaluation of Long Term Reliability and Safe Operating Area of 15 kV SiC PiN Diodes during Ultra-High Current Pulsed Conditions
  Hirsch, E.; Schrock, J. A.; Lacouture, S.; Bilbao, A.; Bayne, S.; Giesselmann, M.; O’Brien, H.; Ogunniyi, A., "Evaluation of Long Term Reliability and Safe Operating Area of 15 kV SiC PiN Diodes during Ultra-High Current Pulsed Conditions," IEEE International Power Modulator and High Voltage Conference (IPMHVC), accepted for publication, 5-6 July 2016.
Abstract:  Not Available
+ Simulation and Design Trade-Off Analysis of 15 kV SiC SGTO Thyristor during Extreme Pulsed Overcurrent Conditions
  Schrock, J. A.; Hirsch, E.; Bilbao, A.; Lacouture, S.; Ray, W.; Bayne, S.; Giesselmann, M.; O’Brien, H.; Ogunniyi, A., "Simulation and Design Trade-Off Analysis of 15 kV SiC SGTO Thyristor during Extreme Pulsed Overcurrent Conditions," IEEE International Power Modulator and High Voltage Conference (IPMHVC), accepted for publication, 5-6 July 2016.
Abstract:  Not Available
Publication Year:  2015
+ Analysis of a tunable electrically small antenna
  B. Esser, S. Beeson, J. Dickens, J. Mankowski and A. Neuber, "Analysis of a tunable electrically small antenna," 2015 IEEE Pulsed Power Conference (PPC), Austin, TX, 2015, pp. 1-3.
Abstract:  A tunable, metamaterial-inspired, electrically small antenna topology is evaluated for a possible future use as the principle radiating element in a mobile Ionospheric Heating (MIH) system. The RF source signal is fed via a 50 Ω coaxial cable into a small semi-loop antenna (SLA). This inductively couples to a capacitively loaded loop (CLL) providing a natural 50 Ω match to the source. The resonant frequency of the antenna can be adjusted by varying the capacitance of the CLL via inserting a large permittivity dielectric. A simplified circuit model is used to show that the resonant frequency can be tuned between 40-100 MHz. Also, the maximum power handling capabilities achievable with this antenna topology at frequencies relevant to ionospheric heating (~ 10 MHz and below) are estimated.

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+ Analysis of advanced 20 kV/20 A silicon carbide power insulated gate bipolar transistor in resistive and inductive switching tests
  A. V. Bilbao, J. A. Schrock, W. B. Ray, M. D. Kelley and S. B. Bayne, "Analysis of advanced 20 KV/20 a silicon carbide power insulated gate bipolar transistor in resistive and inductive switching tests," 2015 IEEE Pulsed Power Conference (PPC), Austin, TX, 2015, pp. 1-3.
Abstract:  The power density of pulsed power systems can be increased with the utilization of silicon carbide power devices. With the latest developments in manufacturing techniques, the fabrication of insulated gate bipolar transistor (IGBT) devices with blocking voltages as high as 20 kV are now possible. A complete practical understanding of ultra-high voltage silicon carbide device switching parameters is not yet known. The purpose of this research is to show switching parameters extracted from inductive and resistive switching tests performed on state of the art 20 kV silicon carbide IGBTs. Resistive switching tests were used to extract device rise time, fall time, turn-on delay, turn-off delay and conduction losses. Double pulsed inductive switching tests were used to extract turn-on and turn-off switching energies and peak power dissipation. The data was obtained at case temperatures from 25 C to 150 C.

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+ Analysis of carrier lifetime effects on HV SIC PiN diodes at elevated pulsed switching conditions
  A. A. Ogunniyi et al., "Analysis of carrier lifetime effects on HV SIC PiN diodes at elevated pulsed switching conditions," 2015 IEEE Pulsed Power Conference (PPC), Austin, TX, 2015, pp. 1-6.
Abstract:  Future Army power systems will require utilizing high-power and high-voltage SiC devices in order to meet size, weight, volume, and high power density for fast switching requirements at both component and system levels. This paper presents the modeling and simulation of a high voltage (>12kV) silicon carbide PiN diode for high action pulsed power applications. A model of a high power PiN diode was developed in the Silvaco Atlas software to better understand the extreme electrical stresses in the power diode when subjected to a high-current pulse. The impact of carrier lifetime on pulsed switching performance of silicon carbide (SiC) PiN diode was investigated.

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+ Analysis of GaN power MOSFET exporsure to pulsed overcurrents
  W. B. Ray et al., "Analysis of GaN power MOSFET exporsure to pulsed overcurrents," 2015 IEEE Pulsed Power Conference (PPC), Austin, TX, 2015, pp. 1-5.
Abstract:  The advancement of wide bandgap semiconductor materials has led to the development of Gallium Nitride (GaN) power semiconductor devices, specifically GaN Power MOSFETs. GaN devices have improved characteristics in carrier mobility and on-state resistance compared to Silicon solid state switches. With the development of these new power semiconductor devices a need was established to understand the behavior of the devices switching performance under stress, with regards to situations in pulsing circuits. Through the examination of the switching characteristics of GaN devices, the results can be used for the improvement of advanced pulsing circuit design with GaN solid state switches. In this paper the authors develop a test bed to expose the GaN Power MOSFETs to single and repetitive pulsed overcurrents. The test bed was developed using a Pulse Ring Down board in a radially symmetric configuration to minimize the total equivalent inductance and resistance. The test bed switches the GaN MOSFET with low impedance between the DC bus and ground to induce the stress the MOSFET experiences during pulsed overcurrents. The DC characteristics were measured between switching sets to reveal characteristic signs of potential degradation and failure modes due to pulsed overcurrents. The single and repetitive pulse switching characteristics are captured, analyzed, and shown.

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+ Characterization of the Optical Properties of GaN:Fe for High Voltage Photoconductive Semiconductor Switch Applications.
  V. Meyers, D. Mauch, J. Mankowski, J. Dickens, A. Neuber, "Characterization of the Optical Properties of GaN:Fe for High Voltage Photoconductive Semiconductor Switch Applications,", 2015 IEEE Pulsed Power Conference, pp. 1-4
Abstract:  The optical properties of bulk semi-insulating GaN:Fe are obtained to assess its future suitability as a high voltage photoconductive semiconductor switch (PCSS). The material properties of GaN:Fe hold significant promise to improve devices for pulsed power and other applications. Growth techniques of bulk GaN:Fe, which have hitherto been largely insufficient for commercial applications, are nearing the point that anticipatory characterization research is warranted. In this paper, the optical constants of bulk GaN:Fe (refractive index, absorption coefficient, and off-state dielectric function) were determined by optical reflection/transmission analysis. The results of this analysis are compared with a similar treatment of bulk 4H-SiC as well as possible elements of PCSS housing: Sylgard 184 elastomer, and EFI 20003/50013 electrical potting epoxy. The data presented provide foundational material characterization to enable assessment of the feasibility of GaN:Fe as a practical high voltage PCSS material. Beyond basic materials research, these properties inform design optimization in PCSS construction and implementation.

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+ Development of secondary breakdown circuit for DV/DT analysis of SIC devices
  J. A. Schrock et al., "Development of secondary breakdown circuit for DV/DT analysis of SIC devices," 2015 IEEE Pulsed Power Conference (PPC), Austin, TX, 2015, pp. 1-5.
Abstract:  Silicon carbide (4H-SiC) is a leading option for increasing the power density of pulsed power and power electronic systems1, 2. SiC devices used in high voltage switching applications experience high dV/dt due to fast switching transients. Under high dV/dt conditions the devices can exhibit spurious turn-ON. For SiC devices to achieve widespread acceptance the dV/dt limit must be established. To measure the dV/dt limit, a circuit comprised of four silicon avalanche BJTs operating in secondary breakdown was constructed. This circuit is capable of generating dV/dts well in excess of what SiC unipolar and bipolar devices might be exposed to in typical applications. Two SiC diodes in an OR configuration are used to perform a comprehensive dV/dt analysis as a function of dc bias. Using this experimental setup dV/dts up to 200 V/ns were applied to SiC MOSFETs, and the induced gate to source voltage was measured. Preliminary dV/dt results achieved with the secondary breakdown circuit are shown for a range of dc biases.

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+ Evaluation and comparison of 1200-V/285-A silicon carbide half-bridge MOSFET modules
  M. D. Kelley, A. V. Bilbao, W. B. Ray, J. A. Schrock and S. B. Bayne, "Evaluation and comparison of 1200-V/285-A silicon carbide half-bridge MOSFET modules," 2015 IEEE Pulsed Power Conference (PPC), Austin, TX, 2015, pp. 1-4.
Abstract:  Silicon Carbide (4H-SiC) is a state-of-the-art solution for increasing the energy density of pulsed power and power electronics. High power SiC MOSFET modules have only recently become commercially available; for widespread acceptance further device characterization and reliability testing is necessary. The purpose of this work is to establish and compare device characteristics for two SiC power modules. Of the two modules tested, one contained Cree die and the other Rohm die. The device characteristics presented for the two modules are switching losses (EON & EOFF) and on-state resistance (RDS(ON)). EON, EOFF, and RDS(ON) were measured at 25°C and 125°C. The RDS(ON) of the two modules was determined to be approximately equal; however, the SiC module containing the Cree die yielded significantly lower turn-on and turn-off switching losses. The measurements presented in this work demonstrate SiC power modules are a leading solution for high energy density applications.

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+ Extraction of Safe Operating Area and long term reliability of experimental Silicon Carbide Super Gate Turn Off Thyristors
  S. Lacouture et al., "Extraction of Safe Operating Area and long term reliability of experimental Silicon Carbide Super Gate Turn Off Thyristors," 2015 IEEE Pulsed Power Conference (PPC), Austin, TX, 2015, pp. 1-4.
Abstract:  While Silicon Carbide (SiC) based power switching elements are starting to appear that are able to perform better than their Si counterparts in terms of voltage hold off, current density and operating temperature, the material is still relatively new in the semiconductor arena, and although new device designs are simulated extensively before being committed to fabrication, there is often a large discrepancy between actual device performance and simulated results. Manufacturers certainly carry out some electrical testing of these quasi experimental components, but there is a dearth of information pertaining to Safe Operating Area (SOA) and device longevity. Texas Tech University's Center for Pulsed Power and Power Electronics, in cooperation with Army Research Lab, has carried out extensive long term, high - energy testing of SiC Super Gate Turn Off Thyristors (SGTOs) produced by Cree Inc. To conduct this extremely high volume testing at high energy levels, an automated test bed was designed that pulses the devices for an arbitrary number of cycles and alternately switches the device to a low energy characterization system, with all waveforms and current - voltage characteristics recorded. Approximately 350,000 high energy cycles on various SGTOs have been recorded. From this large database of results, actual SOA at high cycle count (>>10,000 pulses) has been extracted for the devices. With each cycle's waveforms recorded, and the devices' characteristics traced at chosen intervals, several distinct changes in these parameters have been found to inevitably herald the imminent failure of a device. The most common change is in the gate - anode junction, where curve traces show a leaking, almost resistive behavior immediately before the junction becomes forward biased. As the system is completely automated, and limits can be set to halt a test sequence upon being broached, several devices have been brought to the brink of failure - an event that is usually cat- strophic, physically destroying the device - to be examined by the manufacturer.

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+ Protective networks for high voltage power supplies for pulsed power loads
  M. G. Giesselmann and A. Bilbao, "Protective networks for high voltage power supplies for pulsed power loads," 2015 IEEE Pulsed Power Conference (PPC), Austin, TX, 2015, pp. 1-6.
Abstract:  We are reporting on a comprehensive study on protective de-coupling networks for High Voltage (HV) pulsed power charging supplies. Typically HV power supplies charge large capacitor banks [1, page 3], [2, page 4], which are rapidly discharged into a pulsed power load. Even during a normal discharge, this can put severe stress on the power supply if it is not properly decoupled from the load. A fault at the load capacitor such as a flashover resulting in a ringing discharge with voltage reversal would put even more stress on the power supply, since the load capacitor could discharge through the rectifier diodes in forward direction. In such a case the output rectifier of the power supply could be instantaneously destroyed. Protective networks between the power supply and the load can prevent such damage but may limit the efficiency as well as the available power output and rep-rate of the HV power supply. We are reporting on a number of protective networks including combinations of resistors, inductors, and diodes that can be placed between the output of the power supply and the load. We are also considering the effects of parasitics and the surge I2t action integral [3, Page 20] of the output rectifiers of the power supply to arrive at guidelines for optimal system protection.
Publication Year:  2014
+ Large chip area SiC PiN diodes demonstrated for thyristor protection in a pulsed system
  O'Brien, Heather K; Shaheen, William; Ogunniyi, Aderinto; Scozzie, Charles; Cheng, Lin; Hinojosa, Miguel; Lawson, Kevin; Lacouture, Shelby; Bayne, Stephen; ",Large chip area SiC PiN diodes demonstrated for thyristor protection in a pulsed system,2014 IEEE International Power Modulator and High Voltage Conference (IPMHVC),,,538-541,2014,IEEE
Abstract:  Asymmetric thyristors require protection from voltage and current reversals in high-inductance capacitor discharge systems. Silicon carbide (SiC) PiN diodes capable of blocking up to 16 kV were demonstrated to have the high-current capability to transmit forward pulse current in a series configuration with a thyristor, and to clamp reverse current in an anti-parallel configuration. In series with a thyristor, diodes were switched 1000 pulses at a single-shot rate at 2000 A peak current (3.8 kA/cm2 over anode area and 2100 A2s per pulse) without any notable increases in forward voltage or reverse leakage current. In the reverse clamp configuration, a parallel pair of PiN diodes was demonstrated to block 12 kV charge on the capacitor bank, then clamp a total of 4200 A current reversal with good parallel current sharing. These evaluations demonstrate that for high current density pulsing above 10 kV, individual 16 kV PiN diodes yield lower on-state voltage loss (16 V at 2000 A) than series-stacked assemblies of 9 kV SiC PiN diodes or 6 kV Si diodes.

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+ Modular Marx generator for dV/dt testing of power semiconductor devices
  W. B. Ray, J. A. Schrock, K. Lawson and S. B. Bayne, "Modular Marx generator for dV/dt testing of power semiconductor devices," 2014 IEEE International Power Modulator and High Voltage Conference (IPMHVC), Santa Fe, NM, 2014, pp. 691-693.
Abstract:  A solid-state modular Marx Generator was designed for the purpose of testing the dV/dt capability of Power Semiconductor devices. The Marx Generator is capable of producing up to 1 kV voltage transients with rise times on the order of 10-nanoseconds. This capability to do variable voltage amplitude leads to customizable dV/dt tests. The solid-state modular design will be covered in detail within the paper. The solid-state construction allows for this adjustable dV/dt rating through the utilization of multiple modular stages of Power MOSFETs. These Power MOSFETs have a lower voltage blocking ability, but faster switch closing times. The different modules are controlled through the use of fiber-optic links. These links signal the floating Gate Driver circuitry to synchronize their switch closing time. The floating Gate Driver utilizes isolated switch-mode DC-DC converters to supply the power needed to charge the MOSFET gates, from one ground-referenced power source. The Marx Generator uses high voltage Silicon Carbide Schottky Diodes for the voltage blocking elements when the individual modular stages trigger. The lack of reverse recovery for these high voltage SiC Diodes enables the fast voltage transients that are requisite for dV/dt ranges needed to test Power Semiconductor devices.

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+ Ruggedness evaluation of 56mm2, 180 A SiC DMOSFETs as a function of pulse repetition rate for high power applications
  K. Lawson et al., "Ruggedness evaluation of 56mm2, 180 A SiC DMOSFETs as a function of pulse repetition rate for high power applications," 2014 IEEE 26th International Symposium on Power Semiconductor Devices & IC's (ISPSD), Waikoloa, HI, 2014, pp. 301-304.
Abstract:  Modern power electronics systems try to maximize power density and efficiency. As such, the active switch is required to safely handle very stressful transient conditions. A 56 mm2, 180 A, SiC DMOSFET manufactured by Cree Inc. is evaluated by electrically stressing the device in a RLC ring-down test system capable of producing peak current in excess of 600 A (>3X rated current) and di/dt's as high as 860 A/μs. The device was hard-switched 5,000 times at repetition rates of 1, 2, 5, and 10 Hz for a total of 20,000 switching events. The device characteristics were monitored every 1,000 shots on a high power curve tracer to determine device degradation. The devices showed no changes in blocking characteristics and minimal changes in on-state characteristics due to shifts in the threshold voltage after 20,000 hard switching events. The threshold voltage shifts over the test period are minimal with a +/- 93 mV deviation from the average of 4.39 V. With the stability of the threshold voltage, on-state characteristics, and blocking characteristics; this shows that this device would perform reliably within commercial applications that include stressful switching conditions.

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Publication Year:  2011
+ Advanced Imaging of Pulsed Atmospheric Surface Flashover
  A. Fierro, G. Laity, L. Hatfield, J. Dickens, A. Neuber, "Advanced Imaging of Pulsed Atmospheric Surface Flashover," 18th IEEE International Pulsed Power Conference, June 19th - 23rd, Chicago, IL, (2011).
Abstract:  Vacuum Ultraviolet (VUV) radiation is commonly thought to enhance streamer formation, as it is energetic enough to cause photoionization in the gaseous volume. Light with wavelengths below 180 nm, i.e. VUV, is highly absorbed in the atmosphere which increases the difficulty of measuring any VUV emission from gaseous breakdown at atmospheric pressure. Nevertheless, VUV emission from pulsed surface flashover at atmospheric conditions was previously recorded at Texas Tech. A second generation system was designed to image VUV and visible emission directly while also preserving the spatial profile. The visible emission is imaged through an air-side focused ICCD, while VUV emission is imaged through a vacuum spectrograph. The variable length gap was excited with a pulser designed for a 100 ns rise time and 50 kV peak output. Captured images of visible light emission from streamers produced in oxygen are diffuse whereas nitrogen produces streamers that are segmented. VUV spatial images taken in oxygen reveal stronger emission closer to the cathode region, while nitrogen produces a more distributed intensity profile across the gap. While MgF2 enabled transmission and measurement of VUV, streamer characteristics recorded in the visible light spectrum of surface flashover on BK7 dielectric windows were also investigated. In this paper, the observed streamer images in both visible and VUV wavelength range will be discussed as it relates to surface flashover at atmospheric pressure.

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+ Compact Electro-Explosive Fuse Optimization for a Helical Flux Compression Generator
  J. C. Stephens, A. A. Neuber, J. C. Dickens, M. Kristiansen, "Compact Electro-Explosive Fuse Optimization for a Helical Flux Compression Generator," to be published in Proceedings of the 18th IEEE International Pulsed Power Conference, June 19th - 23rd, Chicago, IL (2011)
Abstract:  This paper presents the optimization of a compact electro-explosive fuse designed for the power conditioning system to be driven by a helical flux compression generator (HFCG). An electro-explosive fuse interrupts the current flow from the HFCG through a storage inductor on a 50 to 100 ns timescale inducing a voltage large enough to close a peaking gap, which commutates the energy in the storage inductor into a 20 Ohm load at voltage levels above 200 kV. Experimental data has revealed that electro-explosive fuses with wires in closer proximity to one another have consistently produced lower pulsed voltages than fuses with larger wire spacings. This paper addresses possible factors that might contribute to this drop in performance. An electro-magnetic field solver is used to model the current redistribution in the fuse wires. The experimentally observed performance of compact fuses with varying wire spacings is presented.

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+ COMSED 2 - Recent Advances to an Explosively Driven High Power Microwave Pulsed Power System
  M. A. Elsayed, A. A. Neuber, A. J. Young, J. W. Walter, C. S. Anderson, S. L. Holt, J. R. Korn, M. Kristiansen, "COMSED 2 - Recent Advances to an Explosively Driven High Power Microwave Pulsed Power System," to be published in Proceedings of the 18th IEEE International Pulsed Power Conference, June 19th - 23rd, Chicago, IL
Abstract:  Continued efforts at the Center for Pulsed Power and Power Electronics at Texas Tech University have led to improvements to the design, testing, and performance of a high power microwave (HPM) system, which is sourced by Lithium-ion Polymer batteries, a polypropylene capacitor, and high energetics. An indirectly seeded two-stage helical flux compression generator (HFCG) produces electrical energies in the kilo-Joule regime into a low impedance inductive load, varying from 2 μH to 3 μH. This high current output of the explosively driven generator is conditioned with a pure silver-wire-based electro-explosive opening switch, which reaches voltage levels in excess of 300 kV into a 18 Ohm load. Upon reaching levels high enough to close an integrated peaking switch, this high voltage is sufficient to drive a reflex triode virtual cathode oscillator, also known as a Vircator, into radiation. The Vircator employed in the system has reached microwave radiation levels well over 100 Megawatts from a cavity volume of less than 5 Liters at a microwave frequency of a few GHz. The complete system is governed through a microcontroller that regulates seed and detonator charging levels as well as discharge times using built-in feedback diagnostics. The complete system aforementioned is constrained to 15 centimeter diameter and measures 183 centimeter in length with an overall volume of less than 34 Liters. No external power or vacuum pumping for the HPM tube is required. This report will discuss recent design advancements and improvements on the HPM system and its sub-components that include the compact seed source, HFCG, and the power conditioning system. Improved safety features implemented as well as novel diagnostic integration will be discussed as well.

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+ Delay Time Distribution of High Power Microwave Surface Flashover
  J. Foster, H. Krompholz, A. Neuber, "Delay Time Distribution of High Power Microwave Surface Flashover," to be published in Proceedings of the 18th IEEE International Pulsed Power Conference, June 19th - 23rd, Chicago, IL (2011)
Abstract:  Breakdown phenomena in a high power microwave (HPM) system present unique obstacles for the further development of HPM technology. The non-uniformity of a high frequency electric field and the statistics associated with breakdown in general along with the stochastic nature of naturally occurring electron generating mechanisms introduce significant challenges for predicting and preventing breakdown occurrences within a HPM system. An experiment consisting of an S-band multi-megawatt HPM pulse is used for observing an alternating field induced plasma sheath across a dielectric surface. In order to minimize experimental deviations, a continuous UV lamp is used to provide a constant source of initiatory electrons through the process of photoemission. This reduces the waiting time for flashover initiating electrons to appear, however, primarily due to avalanche statistics, variations are still observed. A statistical model that uses an exponential distribution sampling procedure was developed to predict the surface flashover delay times for a variety of conditions. A supporting experiment that uses a continuous UV lamp and a DC electric field is used for measuring low current due to photoemission from the dielectric window. An explanation of the model describing these phenomena is presented along with a comparison of current measurements from the supporting experiment.

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+ Diagnostic Measurements on Explosive Emission Cathodes Operating at High Current Densities and UHV Pressures
  C. F. Lynn, J. Walter, A. Neuber, M. Kristiansen, "Diagnostic Measurements on Explosive Emission Cathodes Operating at High Current Densities and UHV Pressures," to be published in Proceedings of the 18th IEEE International Pulsed Power Conference, June 19th - 23rd, Chicago, IL (2011)
Abstract:  Not Available
+ Guest Editorial, IEEE Transactions on Dielectrics and Electrical Insulation
  A. Neuber, B. M Novac, Guest Editorial, IEEE Transactions on Dielectrics and Electrical Insulation 18, pp. 937-937 (2011).
Abstract:  Not Available

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+ Improvements to a Small Scale Linear Transformer Driver
  D. W. Bolyard, A. Neuber, J. Krile, M. Kristiansen, "Improvements to a Small Scale Linear Transformer Driver," to be published in Proceedings of the 18th IEEE International Pulsed Power Conference, June 19th - 23rd, Chicago, IL (2011)
Abstract:  A linear transformer driver (LTD) is being constructed at Texas Tech University's Center for Pulsed Power and Power Electronics with the goal to achieve roughly 100 ns pulse width into an 18 Ohm load and energy densities similar to or greater than a previously designed and built 500 J compact Marx generator. A single experimental LTD stage, previously constructed, tested, and reported on by TTU, has undergone several improvements as well as the inclusion of additional diagnostics. Testing at a charging voltage of 14 kV into a 1.7 Ω resistive load has experimentally achieved a 10% to 90% risetime of ~60 ns, peak voltage of 9.2 kV, peak current of 5.5 kA, and instantaneous power of 50.6 MW. Simulations of the LTD stage correlate closely with the experimental results. Extrapolating the simulations to the final desired charging voltage indicate peak voltages and peak currents exceeding 15 kV and 10 kA respectively, with instantaneous power greater than 150 MW from a single LTD stage. The design for a multi-stage LTD using magnetic cores with a flux swing of 6 kV-μs will be presented. Improvements in diagnostics and modeling of the LTD will also be discussed as well.

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+ Initial Anode Optimization for a Compact Sealed Tube Vircator
  J. Walter, J. Vara, C. Lynn, J. Dickens, A. Neuber, M. Kristiansen, "Anode Optimization for a Compact Sealed Tube Vircator," to be published in Proceedings of the 18th IEEE International Pulsed Power Conference, June 19th - 23rd, Chicago, IL (2011)
Abstract:  During the development and optimization of a compact sealed tube virtual cathode oscillator (vircator) at Texas Tech University, it has become apparent that processes at the anode have a significant impact on tube performance. The impact of the high energy, high current density (100-200 A/cm2 or higher) beam on the anode will cause outgassing, plasma production, and anode melting and material ejection. The emitted material expands, eventually impacting the anode transparency and (combined with the plasma formed at the cathode) shorting out the anode-cathode gap. This expansion limits the maximum radiated pulse width, and can also limit the peak output power. The residual evolved gas also negatively impacts the maximum repetition rate of the tube. An effort is underway to study the thermal behavior, gases evolved, and transparency versus time for different vircator anode materials and material treatments. Several different anode materials are under investigation, including stainless steel, copper tungsten, tantalum, nickel, and molybdenum. The effect of different treatments on the anodes before tube assembly is also being studied. The gases that are evolved during operation have been characterized utilizing pressure and residual gas analyzer measurements. The pre-shot background pressure in the tube is in the ultra-high vacuum range (10-8 to 10-9 Torr), and the vircator is not pumped on during firing. The data collected for the different materials is presented.

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+ Investigation of the Transmission Properties of High Power Microwave Induced Surface Flashover Plasma
  S. Beeson, J. Foster, J. Dickens, A. Neuber, "Investigation of the Transmission Properties of High Power Microwave Induced Surface Flashover Plasma," to be published in Proceedings of the 18th IEEE International Pulsed Power Conference, June 19th - 23rd, Chicago, IL (2011)
Abstract:  When dealing with the propagation of High Power Microwaves (HPM), special precautions must be used to prevent the onset of plasma generation. In this paper, we investigate the plasma located on the high pressure side of the dielectric boundary separating the vacuum environment of the microwave source from the high pressure environment of the transmitting medium, e.g., atmosphere. Because the collisional ionization rates are a monotonously increasing function of Eeff/p in the range of interest, the effective electric field normalized with pressure, implementation of HPM in high altitude (low pressure) environments are subject to dielectric breakdown due to this generated plasma, more than at sea-level altitudes. Dielectric breakdown causes the interruption in transmission of electromagnetic radiation due to the reflection and absorption properties of the plasma generated on the dielectric surface. In this paper, transmission, reflection, and absorption data is presented for plasma generated under various pressures ranging from 5 to 155 torr in N2 and air environments. In addition, seed electrons from UV illumination of the dielectric surface and physical vapor deposited metallic points are implemented and their implications to the overall transmission properties are discussed.

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+ Nanosecond-Scale Spectroscopy of Vacuum Ultraviolet Emission from Pulsed Atmospheric Discharges
  G. Laity, A. Neuber, A. Fierro, J. Dickens, L. Hatfield, "Nanosecond-Scale Spectroscopy of Vacuum Ultraviolet Emission from Pulsed Atmospheric Discharges," to be published in Proceedings of the 18th IEEE International Pulsed Power Conference, June 19th - 23rd, Chicago, IL (2011)
Abstract:  This paper describes a 2nd-generation system for directly studying the emission of vacuum ultraviolet (VUV) light from pulsed dielectric surface flashover at atmospheric pressure. The role of self-produced VUV emission (i.e. energies greater than 7 eV) on photo-ionization processes during the early nanoseconds of pulsed discharges is virtually unexplored, and yet could be a significant factor in the physics of fast breakdown of directed energy systems (such as MW-class high power microwave devices) in the aerospace community. First generation experiments at Texas Tech University have shown that VUV emission corresponding to nitrogen and oxygen excitation in the energy range 8 - 10 eV is easily produced, but the use of MgF2 optics inhibited future work with existing hardware due to the transmission cutoff of this dielectric material and chromatic aberration if used as a lensing medium. In an effort to enhance the detection capabilities of our hardware in the wavelength range from 115 - 135 nm, the current system utilizes a custom designed set of off-axis parabolic MgF2-Aluminium coated mirrors as the primary focusing element. High resolution spectroscopy with the upgraded system resulted in the observation of the nitrogen doublet at 149.5 nm, leading to a better fit for the appropriate line broadening parameters for an approximate 10 eV Boltzmann electronic temperature. Evidence of self-absorption for HI (121.5 nm) provides new insight into the generation of space charge in these plasma structures, which has been investigated quantitatively in both SF6-H2 and N2-H2 mixtures.

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+ Re-distribution of MRSA (Methicillin-resistant Staphylococcus aureus) during the laundering (normal machine washing) process on towel
  A. Laury, K. Fermin, D. Stull, A. Neuber, C. Brooks, T. Brashears, C. Alvarado, M. Brashears," Re-distribution of MRSA (Methicillin-resistant Staphylococcus aureus) during the laundering (normal machine washing) process on towels," ASM 2011, May 20th - 24th, New Orleans, LA.
Abstract:  Not Available
+ Reduction of MRSA (Methicillin-resistant Staphylococcus aureus) on towels utilizing Targeted Directional Microwave technology
  A. Laury, K. Fermin, D. Stull, A. Neuber, C. Brooks, T. Brashears, C. Alvarado, M. Brashears," Reduction of MRSA (Methicillin-resistant Staphylococcus aureus) on towels utilizing Targeted Directional Microwave technology," ASM 2011, May 20th - 24th, New Orleans, LA.
Abstract:  Not Available
+ Reduction of Salmonella on jalapeño peppers, peanuts, and dry dog food utilizing targeted directional microwave technology
  A. Laury, K. Fermin, D. Stull, A. Neuber, C. Brooks, C. Alvarado, T. Brashears, M. Brasheers, "Reduction of Salmonella on jalapeño peppers, peanuts, and dry dog food utilizing targeted directional microwave technology," Annual Meeting of the International Association for Food Protection, July 31 - August 3, Milwaukee, WI, 2011
Abstract:  Not Available
+ Temperature Dependence of Ferrimagnetic Based Nonlinear Transmission Line
  J.-W. B. Bragg, J. Dickens, A. Neuber, "Temperature Dependence of Ferrimagnetic Based Nonlinear Transmission Line," to be published in Proceedings of the 18th IEEE International Pulsed Power Conference, June 19th - 23rd, Chicago, IL (2011)
Abstract:  Ferrite loaded nonlinear transmission lines (NLTLs) are able to act as high power microwave sources, utilizing the nonlinearities present in ferrimagnetic materials and the excitation of damped gyromagnetic precession at high incident power levels. Ferrimagnetic properties depend greatly on operating temperatures; therefore, there exists a need to know the ideal temperature at which to operate ferrite loaded NLTLs. Ferrites are chilled or heated to a certain temperature for a time suitable to allow internal ferrite temperature uniformity. Experimental temperatures ranged from approximately -20 °C up to 150 °C, which is slightly above the Curie temperature of the loaded ferrites. This temperature range allows observation of precession dependence on temperature while maintaining ferrimagnetic properties and a single look at the behavior outside the ferrimagnetic regime. Above the Curie temperature the loaded ferrites become paramagnetic and lose ferrimagnetic properties. The design, testing, and results are detailed for an NLTL measuring 0.3 m length and ferrite inner and outer diameters of 3 mm and 6 mm respectively. Figures comparing output waveforms at different temperatures, output power versus temperature, and output frequency versus temperature are shown.

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+ The Effects of Stator Insulation Material and Methods of Fabrication on the Performance of Compact Helical Flux Compression Generators
  C. S. Anderson, A. A. Neuber, M. A. Elsayed, A. J. Young, "The Effects of Stator Insulation Material and Methods of Fabrication on the Performance of Compact Helical Flux Compression Generators," to be published in Proceedings of the 18th IEEE International Pulsed Power Conference, June 19th - 23rd, Chicago, IL (2011)
Abstract:  Helical Flux Compression Generators, HFCGs, are powerful high current sources for pulsed power applications. Due to the single shot nature of HFCGs, electrical output reproducibility is of great importance. One factor known to contribute to unpredictable performance is mechanical inconsistencies introduced during manufacturing of the stator. In an attempt to minimize these deviations during productions, two different winding forms for stator coils, designed to ensure repeatable generator dimensions, turn and coil pitch, were investigated. The differences between the methods were quantified by comparison of measurements made of the physical parameters of the coil (i.e. radius, inductance, etc.), as well as analysis of experiments conducted with the HFCGs fired into a 3 μH load inductor. With any particular fabrication method, the stator insulation material has a distinct impact on generator operation. Quad-built Polyimide coated magnet wire as stator insulation material and Teflon Fluorinated Ethylene Propylene (FEP) as field coil insulation material were investigate to improve HFCG performance. Insulation testing was carried out by firing HFCGs into the inductive load mentioned above. Experimental data and analysis, as well as conclusions on insulation material, will be presented along with a brief discussion of the optimum fabrication method.

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Publication Year:  2010
+ A Low Impedance 500 kV 2.75 kJ Marx Generator as Testbed for Vacuum Diodes
  C. Lynn, A. Neuber, E. Matthews, J. Walter, M. Kristiansen, "A Low Impedance 500 kV 2.75 kJ Marx Generator as Testbed for Vacuum Diodes," 2010 IEEE International Power Modulator and High Voltage Conference, May 23 - 27, 2010 in Atlanta, GA.
Abstract:  A low impedance Marx generator was developed as part of a test bed for vacuum diodes of various electrode materials and geometries. The generator supplies sufficient energy to initiate and sustain the typically unwanted plasma formation within the diode; which facilitates the observation of the plasma, current uniformity, and electron current densities of various diode structures. The generator consists of ten stages; each stage utilizes a 220 nF 50 kV capacitor, with a series inductance of ~20 nH. When charged to the rated voltage of the capacitors the energy density of the complete generator with case, spark gaps, insulation, etc., is 19.2 mJ/cm3; this is roughly the energy density of a typical ceramic doorknob capacitor without any supporting structure or isolation. The energy density of the capacitors utilized in the Marx generator by themselves is 104 mJ/cm3. Fired into a low inductance short, the ringing frequency was measured to be 1.4 MHz resulting in an output impedance of 5.2 Ω. Erection of the Marx required adding forward feeding capacitors as the stray capacitance to ground is smaller than the capacitance (~60 pF) of the low inductance, low profile spark gap switches. The design and construction of this generator are discussed as well as selected experimental results obtained with the generator.

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+ An Investigation of Pulsed High Power Microwave Surface Flashover Initiation in Atmospheric Conditions
  J. Foster, M. Thomas, J. Krile, H. Krompholz, A. Neuber, "An Investigation of Pulsed High Power Microwave Surface Flashover Initiation in Atmospheric Conditions," 37th IEEE International Conference on Plasma Science, June 20th - 24th, Norfolk, VA, (2010).
Abstract:  The production of high power microwaves (HPM) in a vacuum environment for the purpose of radiating into atmosphere requires the use of a dielectric interface to separate the vacuum and atmospheric sides of the radiating structure. For high power to pressure ratios the interface will exhibit surface flashover on the atmospheric side, thus limiting the transmission of microwave power. An experimental setup that utilizes a magnetron operating at 2.85 GHz to produce a 4.5 MW, 3μs pulse propagating in the TE10 mode along with an atmospheric test chamber enables investigating HPM surface flashover phenomena in the presence of various atmospheric conditions. One of the principle parameters measured is the delay time between application of the microwave pulse (50 ns rise time) and the sharp drop in transmitted power due to the flashover plasma formation. Several methods of delay time reduction have been employed to gain a better understanding of the source of breakdown initiatory electrons. For an environment composed of air at, for instance, 155 torr a delay time of 600 ns is observed. Illuminating the dielectric surface with continuous UV radiation reduces the average delay to about 380 ns. An even more distinct reduction in delay time was observed when electric field enhancement was introduced to the window surface via vapor deposition of sub-mm metallic points on the dielectric. These metallic points have proven to reduce the delay time to ~150 ns while increasing the global effective electric field by a factor of ~1.5. This presentation will include an overview of a variety of methods for investigating flashover initiation, including UV radiation and the application of an external DC electric field, as well as the introduction of field enhancing metallic points on the dielectric surface. An analysis of flashover behavior at atmospheric pressures (60-155 torr) in air, argon, and nitrogen will also be given along with an estimation of field enhancement- - factors for various geometries.

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+ Atmospheric Flashover in a Symmetric Electric Field Geometry
  G. Rogers, A. Neuber, L. Hatfield, G. Laity, K. Frank, J. Dickens, "Atmospheric Flashover in a Symmetric Electric Field Geometry," 2010 IEEE International Power Modulator and High Voltage Conference, May 23 - 27, 2010 in Atlanta, GA.
Abstract:  In an attempt to identify the mechanisms leading to pulsed dielectric surface flashover in atmospheric conditions, surface flashover across a magnesium fluoride (MgF2) window was studied. The electrode configuration and the applied pulsed voltage level were chosen such that the generated electric field was symmetric with respect to the centerline between the electrodes. That is, neither electrode was favored with respect to flashover/breakdown initiation. A semiconductor-switched 32 kV pulse with 140 ns rise time was applied to the 8 mm wide flashover gap in air, nitrogen, and oxygen at atmospheric pressure. Fast voltage and current measurements along with nanosecond imaging revealed four stages of flashover development: (1) Onset of a cathode directed streamer with a charge on the order of 100 pC and traveling with a speed of ~1 mm/ns at a macroscopic field level of ~10 kV/cm associated with a slow current rise (on the order of 10-3 A/ns) temporarily augmented by (2) a 5 ns wide current spike at the moment when the streamer reaches the cathode followed by (3) a cathode directed streamer focused toward the center of the flashover gap with a slow rising current leading to (4) a sharp current rise (on the order of 10 A/ns) reaching roughly a circuit limited 45 A about 20 ns after the return strike meets an anode directed streamer. Although present in all tested gases, the current spike at the end of stage (2) is most different for all three gases and having the greatest impact in air.

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+ Compact Magnetically Insulated Transmission Line Oscillator
  Vasiliy Smirnov, Magne Kristiansen, John Mankowski, James Dickens, Andreas Neuber, Lynn Hatfield, Hermann Krompholz, John Walter, "Compact Magnetically Insulated Transmission Line Oscillator", ICOPS 2010, The 37th IEEE International Conference on Plasma Science, June 20 - 24, 2010, Norfolk, Virginia, USA, Page 251.
Abstract:  Not Available
+ COMSED 1 - A Compact, Gigawatt Class Microwave Source Utilizing Helical Flux Compression Generator Based Pulsed Power
  A. Young, A .Neuber, M. Elsayed, J. Korn, J. Walter, S. Holt, J. Dickens, M. Kristiansen, L. Altgilbers, "COMSED 1 - A Compact, Gigawatt Class Microwave Source Utilizing Helical Flux Compression Generator Based Pulsed Power," 2010 IEEE International Power Modulator and High Voltage Conference, May 23 - 27, 2010 in Atlanta, GA. Invited.
Abstract:  Recent progress in the development of a compact, portable, explosively-driven high power microwave source is presented. The envelope to which the system must fit has a 15 cm diameter, which means each sub-system fits within this dimension, with an optimized overall length. The system includes an autonomous prime energy source, which provides the initial energy for a two-stage, flux-trapping helical flux compression generator (FCG). Typical output from the FCG is several kilojoules into a 3 μH inductor. The amplified energy from the generator, after pulse conditioning, is used to drive a virtual cathode oscillator (vircator). Recorded voltages at the vircator with this arrangement were greater than 200 kV in experiments, where radiated output powers of greater than 100 MW have been measured. Voltages of at least 300 kV, with an electrical output power of 4 GW or greater, were generated by the FCG driven pulsed power source into a water resistor load with an impedance similar to the operating impedance of the vircator. A description of each component of the compact microwave source will be given, along with waveforms from tests performed with the components independent of the rest of the system. Data from experiments with the fully integrated microwave system will be shown, and analysis will be offered to detail the performance of the system in its present state.

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+ Effects of Gas Temperature and Gas Mixtures on a Triggered, Sub-ns Jitter, 50 kV, 100 Hz Spark Gap
  Y. Chen, J. Dickens, J. Mankowski, M. Kristiansen, "Effects of Gas Temperature and Gas Mixtures on a Triggered, Sub-ns Jitter, 50 kV, 100 Hz Spark Gap", 2010 IEEE International Power Modulators and High Voltage Conference, Atlanta GA, May 2010.
Abstract:  Recent research efforts at Texas Tech University on impulse antenna phased array have shown that an ideal jitter of a small fraction of the rise-time is required to accurately synchronize the array to steer and preserve the rise-time of the radiated pulse. This has necessitated the need to develop a reliable high voltage, high repetition rate switch that will operate with very low jitter. This manuscript presents the impact gases and gas mixtures have on switch performance which includes recovery rate and in particular jitter. A 50 Ω, 1 nF pulse forming line is charged to 50 kV and provides the low inductance voltage source to test the different gases. Gases tested include N2, dry air, H2, and SF6, as well as N2-H2, N2-SF6, N2-Ar, and gas mixtures containing Kr85. This manuscript will discuss in detail 50 kV, 100 Hz triggered switch operations of such gases. Switch jitter as a result of triggering conditions is also discussed, also including an evaluation of jitter as a function of formative delay in various gases. An evaluation of switch jitter as a function of operation time and gas temperature is also included. Triggering is provided by a solid state opening switch voltage source that supplies ~150 kV, 10 ns rise-time pulses at a rep-rate up to 100 Hz in burst mode. A hermetically sealed spark gap with a Kel-F -PCTFE (PolyCholoroTriFluoroEthylene) lining is used to house the switch and high pressure gas. It is shown that jitter is strongly dependent on the triggering technique, as well as the trigger magnitude, with ionization rates playing an important role. Sub-ns jitter is seen with a variety of gases and gas mixtures with H2 producing the best results. Varying the gas temperature and addition of radioactive sources are seen to improve the switch jitter.

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+ First Results of Streamer Formation During Dielectric Surface Flashover at Atmospheric Conditions
  K. Frank, J. Dickens, L. Hatfield, M. Kristiansen, G. Laity, A. Neuber, G. Rogers, "First Results of Streamer Formation During Dielectric Surface Flashover at Atmospheric Conditions," DPG Spring Meeting of the Atoms, Molecules, Optics, and Plasmas Section, March 8th - 12th, Hannover, Germany, (2010).
Abstract:  Not Available
+ High Power Microwave Surface Flashover Seed Electron Production Methods
  M. Thomas, J. Foster, H. Krompholz, A. Neuber, "High Power Microwave Surface Flashover Seed Electron Production Methods," 2010 IEEE International Power Modulator and High Voltage Conference, May 23 - 27, 2010 in Atlanta, GA.
Abstract:  Surface flashover imposes a fundamental limitation to the magnitude of high power microwaves which can be radiated from the vacuum environment of the source into atmospheric conditions. Providing seed electrons through various methods allows for initiatory conditions to be more closely controlled and the delay time variations to be reduced so that developmental mechanisms can be more closely examined. The experiment uses a coaxial magnetron capable of producing a ~4.5 MW, 3 μs pulse, at 2.85 GHz propagating in the TE10 mode. The pulse rise time measured at the window is reduced using a spark gap pulse steepening technique. The fast rise time pulse propagates through the dielectric into an atmospheric test chamber where various conditions such as gas pressure, type of gas, UV illumination, and charged particle creation by radioactive sources can be controlled. Previous research has shown the significant impacts of UV radiation on the delay time averages and statistical distributions. Surface distributed seeding sources and volume distributed sources will be discussed while the primary focus of this paper will address use of alpha radiation as an ionizing agent. Thus far, a reduction in average delay time by as much as 60% has been achieved at sub-microsecond time scales, which also significantly affected the width of the statistical distributions of the delay time. Alpha particles have a short penetration distance in air which makes them a good candidate for study since the number of electron-ion pars created along the path is large. Analysis of the alpha particles influences will be discussed along with a statistical analysis of breakdown delay in the presence of ionization.

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+ High Power Microwave Surface Flashover Using a Monte Carlo Code
  J. Krile, J. Foster, M. Thomas, H. Krompholz, A. Neuber, "High Power Microwave Surface Flashover Using a Monte Carlo Code," AFOSR Counter High Power Microwaves Meeting, July 29th - 30th, Albuquerque, NM, (2010).
Abstract:  Not Available
+ Influence of Seed Electrons on High Power Microwave Window Flashover
  J. Foster, S. Beeson, M. Thomas, J. Krile, H. Krompholz, A. Neuber, "Influence of Seed Electrons on High Power Microwave Window Flashover," AFOSR Counter High Power Microwaves Meeting, July 29th - 30th, Albuquerque, NM, (2010).
Abstract:  Not Available
+ Magnetic Biasing of Ferrite Filled Nonlinear Transmission Line
  J. Bragg, J. Dickens, A. Neuber, "Magnetic Biasing of Ferrite Filled Nonlinear Transmission Line," 2010 IEEE International Power Modulator and High Voltage Conference, May 23 - 27, 2010 in Atlanta, GA.
Abstract:  Not Available
+ Material Emission Investigation of Explosive Emission Cathodes in Vacuum Sealed Tubes
  J. Parson, J. Dickens, A. Neuber, J. Walter, "Material Emission Investigation of Explosive Emission Cathodes in Vacuum Sealed Tubes," 37th IEEE International Conference on Plasma Science, June 20th - 24th, Norfolk, VA, (2010).
Abstract:  Not Available
+ Microwave Surface Flashover Using Metallic Initiators
  J. Foster, M. Thomas, H. Krompholz, A. Neuber, "Microwave Surface Flashover Using Metallic Initiators," 2010 IEEE International Power Modulator and High Voltage Conference, May 23 - 27, 2010 in Atlanta, GA.
Abstract:  Not Available
+ Modeling Of Compact Explosively-Driven Ferroelectric Generators
  D. Bolyard, A. Neuber, J. Krile, M. Kristiansen, "Modeling Of Compact Explosively-Driven Ferroelectric Generators," 2010 IEEE International Power Modulator and High Voltage Conference, May 23 - 27, 2010 in Atlanta, GA.
Abstract:  Hydrodynamic pressure simulations combined with an empirical algorithm are used to model the open-circuit voltage output of several explosively compressed ferroelectric materials. The empirical algorithm was initially developed using detonating cord containing PETN and a metal driver element to compress the ferroelectric materials while the open-circuit voltage is recorded. A hydrodynamic code suite, CTH from Sandia National Labs, enables calculating Shockwave propagation and localized pressures. The resulting pressure profile in the ferroelectric material is then used as input for an empirically derived algorithm to calculate the predicted open-circuit voltage of the ferroelectric material. This previously developed empirical algorithm exhibited reasonable correlation between experimental and calculated open-circuit output voltages, but began to deviate when more powerful explosives were used. Hence, the amount of explosive material and geometry of the metal drive was varied to produce a wide range of peak pressures, including pressures higher then the maximum of 3.1 GPa previously modeled by the empirical algorithm. This data serves as the base to further develop the empirical algorithm for various ferroelectric materials and to more accurately model the open-circuit output voltage (experimentally observed range, normalized for thickness, of 1.3 to 3.8 kV/mm) over the wide range of applied pressures.

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+ Modular, Compact HV-Capacitor Charger
  Michael G. Giesselmann, Travis T. Vollmer, Larry Altgilbers, "Modular, Compact HV-Capacitor Charger", Proceedings of the 2010 IEEE International Power Modulator and High Voltage Conference, May 23-27, 2010, Atlanta, GA
Abstract:  We are reporting on a new compact high power capacitor charger with modular topology for rep. rated High Power Microwave generators and other Pulsed Power Applications. The charger is capable of using a number of synchronized H-Bridge inverters feeding into a common transformer. The common transformer uses litz wire windings and a nano-crystalline core to reduce losses and AC impedance. The H-Bridge inverter modules are individually controlled using peak current mode control which assures proper current sharing and protects the H-Bridge modules from overload while achieving the maximum current handling capacity. To assure stability of the current loops for peak current mode control, slope compensation is used. Major advancements over previous designs are the ability to use multiple H-Bridge inverters with proper synchronization, improved efficiency through advanced transformer design and improved current mode control.

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+ Monte Carlo Simulation of High Power Microwave Surface Flashover under UV Illumination
  J. Krile, J. Foster, M. Thomas, A. Neuber, "Monte Carlo Simulation of High Power Microwave Surface Flashover under UV Illumination," 2010 IEEE International Power Modulator and High Voltage Conference, May 23 - 27, 2010 in Atlanta, GA.
Abstract:  High Power Microwave (HPM) induced surface flashover is currently being investigated in order to gain a better understanding of the underlying processes involved and reduce the limitations it places on transmittable pulse lengths. The present experimental setup is designed to produce a flashover on the high pressure side of a transmission window without the influence of a triple point. A 2.5 MW magnetron produces a 900 ns pulse at 2.85 GHz with a 50 ns rise time. The experimental setup allows for the control of several parameters including gas pressure, gas composition, and external UV illumination of the window. Diagnostic equipment enables the analysis of incident, reflected, and transmitted power levels with sub-nanosecond resolution. A previously developed Monte Carlo simulation is used to model the processes involved in the flashover discharge formation. This Monte Carlo code is upgraded to account for the occurrence of field induced electron detachment from negative ion clusters within the high field region, >; 10 kV/cm, near the window. The code has also been expanded to include the occurrence of photoelectrons, emitted from the window while under UV illumination. Such illumination of the transmission window was experimentally shown to reduce the time to flashover by over 100 ns in air at 155 torr, and thereby the total pulse energy that can be transmitted. In addition, UV illumination also reduces the variation in flashover delay times from shot to shot, up to 67% in air at 155 torr. The simulation will determine if the observed reductions in delay time and variation can be explained by the addition of initiatory electrons via UV illumination of the surface.

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+ Optimization of a Fuse Opening Switch for a Compact Power Conditioning Unit
  J. Korn, A. Young, A. Neuber, C. Davis, M. Elsayed, M. Kristiansen, L. Altgilbers, "Optimization of a Fuse Opening Switch for a Compact Power Conditioning Unit," 2010 IEEE International Power Modulator and High Voltage Conference, May 23 - 27, 2010 in Atlanta, GA.
Abstract:  The results from an investigation into the performance of a fuse opening switch, to be used as a component of a compact power conditioning unit, PCU, in an explosively driven high power microwave system, is presented. A pulse forming network designed to mimic the current action of a flux compression generator is utilized for these experiments. The investigation focused on the effect of altering fuse parameters, such as the diameter of fuse conductors and conductor winding geometry, on voltage and power levels delivered to a resistive load. Also, experiments were conducted with a thin layer of Semicosil, a commercial silicon material used in slower fusing opening switches, applied to fuse conductors, to investigate the possible advantages of using such a coating. Experiments showed that an increased number of conductor wires (with an approximately constant total cross-sectional area) resulted in similar voltages delivered to the resistive load, and that coating fuse conductors with Semicosil had a negligible effect on power delivery. A detailed description of these experiments will be given, along with data and waveforms illustrating the effects of these parameter variations on power levels delivered to the load.

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+ Optimizing Wire Parameters in Exploding Wire Arrays
  C. Davis, A. Neuber, J. Stephens, A. Young, M. Kristiansen, "Optimizing Wire Parameters in Exploding Wire Arrays," 2010 IEEE International Power Modulator and High Voltage Conference, May 23 - 27, 2010 in Atlanta, GA.
Abstract:  Exploding wire arrays as fast switches are of interest for explosive pulsed power applications utilizing magnetic flux compression. This type of opening switch has proven effective in producing pulses of several hundred kilovolts into vacuum diode loads. The research presented here discusses an exploding wire array capable of producing single digit kilo-joules, 100 nanosecond pulses when driven by a 45 kilo-Amp current with a waveform closely resembling typical magnetic flux compression output. For this specific parameter range, the optimal fuse design was developed based on the experimental behavior of the fuse under variation of parameters such as wire spacing, shielding, and quenching medium. Each fuse is composed of several silver wires arranged in a straight wire cylindrical array and is typically pressurized in a chamber filled with about 0.6 MPa of SF6. The tradeoff between wire spacing and voltage output was addressed by designing four different fuse termination pairs each with a diameter that increased wire spacing from 5 to 20 mm in 5 mm increments. A wire shield test was also conducted as an extension to the wire spacing experiment to uncover any mutual radiative effects between wires on fuse opening behavior. The optimum fuse design, including the optimum fuse wire diameter, will be discussed with a 20 Ohm resistive load as well as a vacuum diode load with similar impedance.

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+ Performance of a Dual-Stage Helical Flux Compression Generator Under Varying Background Gas And Pressure
  M. Elsayed, A. Neuber, A. Young, J. Korn, J. Dickens, M. Kristiansen, C. Lynn, L. Altgilbers, "Performance of a Dual-Stage Helical Flux Compression Generator Under Varying Background Gas And Pressure," 2010 IEEE International Power Modulator and High Voltage Conference, May 23 - 27, 2010 in Atlanta, GA.
Abstract:  Recent efforts at the Center for Pulsed Power and Power Electronics at Texas Tech University have been focused on the development of a compact and explosively driven High Power Microwave, HPM, system. The primary energy source (other than the seed energy source) driving the microwave load in this system is a mid-sized, dual-stage helical flux compression generator, HFCG. The HFCG has a constant stator inner diameter of 7.6 cm, a length of 26 cm, with a working volume of 890 cm3. Testing at the Center has revealed energy gains in the 30's and 40's with output energy levels in the kilo-joules regime into loads of several micro-Henries. Over the last few years, close to one hundred shots have been taken with these generators into various loads consisting of dummy inductive loads, power conditioning systems, and HPM sources. Throughout these tests, the working volume of the HFCG, i.e. the volume in between the wire stator and the explosive-filled aluminum armature, was filled with SF6 at atmospheric pressure. This was primarily done do avoid electrical breakdown in the generator volume during operation, resulting in flux loss. Recent design updates enable pressurizing the generator volume to pressures up to 0.5 MPa, which is needed, for instance, to replace the SF6 with other gases such as air or nitrogen. The performance of the dual-stage HFCG with pressurized working volume (SF6 and N2) is presented in this paper along with an analysis of the maximum electric field amplitude held off in the volume during operation. The design technique to seal the HFCG will also be briefly discussed.

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+ Pulsed Atmospheric Breakdown
  G. Laity, H. Krompholz, A. Neuber, L. Hatfield, K. Frank, A. Fierro, J. Dickens, M. Kristiansen, "Pulsed Atmospheric Breakdown," AFOSR Counter High Power Microwaves Meeting, July 29th - 30th, Albuquerque, NM, (2010).
Abstract:  Not Available
+ Pulsed Breakdown and Flashover at Atmospheric Pressure
  A. Neuber, H. Krompholz, J. Dickens, J. Krile, J. Foster, S. Beeson, M. Thomas, G. Laity, A. Fierro, "Pulsed Breakdown and Flashover at Atmospheric Pressure," AFOSR Counter High Power Microwaves Meeting, July 29th - 30th, Albuquerque, NM, (2010).
Abstract:  Not Available
+ Rapid Charging Seed Source with Integrated Fire Set for Flux Compression Generator Applications
  S. L. Holt, M. A. Elsayed, B. Gaston, J. C. Dickens, A. A. Neuber, M. Kristiansen, "Rapid Charging Seed Source with Integrated Fire Set for Flux Compression Generator Applications," 2010 IEEE International Power Modulator and High Voltage Conference, May 23 - 27, 2010 in Atlanta, GA.
Abstract:  The design and testing of an integrated front-end power and control system for helical flux compression generators (HFCG) is presented. A current up to 12 kiloamps needs to be pushed into the 5.8 microhenry field coil of the HFCG to establish the necessary seed flux for generator operation. This current is created with the discharge of a 5 kilovolt, 50 microfarad metalized polypropylene film capacitor using a single-use semiconductor closing switch. Once peak current/flux is obtained in the seed coil an exploding bridge wire (EBW) detonator is initiated with a discharge from a 1 kilovolt, 500 millijoule capacitor array contained in the compact fire set. Both capacitances, seed and fire set, are charged using a rapid capacitor charger system. The rapid capacitor charger is a solid state step up converter supplied by lithium-ion polymer (LiPo) batteries. It provides the 5 kilovolts and 1 kilovolt dual output voltages required for the compact seed source and compact fire set, respectively. The rapid capacitor charger operates at an average output power of 3 kilowatts and charges both capacitances simultaneously in under 250 milliseconds. The rapid capacitor charger is reusable if protected from the explosive detonation.

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+ Simulation of Cascaded Flux Compression Generators with Conventional Circuit Simulation Software
  A. Young, A. Neuber, M. Kristiansen, "Simulation of Cascaded Flux Compression Generators with Conventional Circuit Simulation Software," The 13th International Conference on Megagauss Magnetic Field Generation and Related Topics, July 06-10, 2010, Nanlin Hotel, Suzhou, China.
Abstract:  Not Available
+ Spectral Analysis of Vacuum Ultraviolet Emission from Pulsed Atmospheric Discharges
  G. Laity, A. Neuber, G. Rogers, K. Frank, L. Hatfield, J. Dickens, "Spectral Analysis of Vacuum Ultraviolet Emission from Pulsed Atmospheric Discharges," 37th IEEE International Conference on Plasma Science, June 20th - 24th, Norfolk, VA, (2010).
Abstract:  Summary form only given. It is commonly accepted that vacuum ultraviolet (VUV) radiation, corresponding to emission from 180 nm to 115 nm and below, is responsible for photoionization contributing to streamer propagation during the initial stages of atmospheric discharges. An experimental setup was constructed to observe the VUV emission of pulsed surface flashover along a dielectric surface between atmosphere and vacuum. However, VUV radiation is highly attenuated in the atmosphere, which makes observation of detailed spectra difficult. For VUV transmission down to 115 nm the light emitted by surface flashover across an MgF2 window (front side of window in air, backside in vacuum) was focused by an MgF2 lens onto the entrance slit of the spectrograph. The high speed detection scheme consists of a VUV sensitive ICCD camera and a photomultiplier, both with nanosecond temporal resolution. Spectra were measured in various gas mixtures at atmospheric pressure with a flashover spark length of about 8 mm with a 35 kV pulsed excitation, and spectral calibration was done utilizing a VUV calibration lamp with a known emission spectrum. Virtually all lines from 115 to 180 nm can be identified as atomic oxygen and nitrogen transitions during flashover in dry air, with most VUV emission occurring during the initial breakdown stage (current rise). The extremely fast decay of VUV emission intensity following this initial stage is evidence of radiationless quenching of the excited energy levels associated with the observed spectral lines. Flashover studies were also performed in pure oxygen and nitrogen environments to reinforce the observed emission trends. Spectroscopy must be carefully detailed, for instance, the Oxygen-I line at 130.2 nm (which corresponds to a ground level transition) is shown to be strongly self absorbed in the atmospheric spark when compared to a similar oxygen emission line at 130.4 nm. Full spectra were simulated using SpectraPlot, a- - temperature dependent spectral software suite developed at Texas Tech. It has been concluded from the comparison of simulated and measured Nitrogen spectra between 140 and 150 nm that the electronic temperature is about 4.5 eV, assuming that the electronic nitrogen energy level population density is Boltzmann distributed. The measured spectra will be discussed in relation to the physics of surface flashover and volume breakdown at atmospheric pressure.

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+ Synchronization of Phased Array Pulsed Ring-down Sources using a GPS based timing system
  Y. Chen, J. Dickens, S. Holt, D. Reale, J. Mankowski, and M. Kristiansen, "Synchronization of Phased Array Pulsed Ring-down Sources using a GPS based timing system", 2010 IEEE International Power Modulators and High Voltage Conference, Atlanta GA, May 2010.
Abstract:  A collaborative effort at Texas Tech University on high power RF transmitters has directly translated to the development of phased array pulsed ring down sources (PRDS). By operating an array of PRDS, peak radiating power on target can theoretically be multiplied by the number of sources. The primary limitation on the application of the array concept is the jitter with which the individual sources can be fired. An ideal jitter of a small fraction of the risetime is required to accurately synchronize the array to steer and preserve the risetime of the radiated pulse. This paper describes in detail the implementation of a GPS based timing system that will synchronize the individual antennas to operate at different geo-locations to function in a coordinated fashion to deliver the peak power of each element to a single position. Theoretical array performance is shown through Monte Carlo simulations, accounting for switch jitter and a range of GPS timing jitter. Each module will include a control unit, low jitter pulser, low jitter spark gap, antenna element, as well as a GPS receiver. The location of each module is transmitted to a central controller, which calculates and dictates when each element is fired. Low jitter in the timing of the GPS reference signal is essential in synchronizing each element to deliver the maxim power. Testing using a preliminary setup using GPS technology is conducted with both 1 pps and 100 pps outputs. Jitter results between modules are recorded to ~10 ns without any correction factors. With the timing and geospatial errors taken into account, the proposed concept will show usable gains of up to several hundred MHz.

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+ Theoretical Performance of a GPS Linked Pulsed Ring Down Array
  D. Reale, J. Mankowski, S. Holt, Y. Chen, J. Walter, and J. Dickens, "Theoretical Performance of a GPS Linked Pulsed Ring Down Array", 2010 IEEE International Power Modulators and High Voltage Conference, Atlanta GA, May 2010.
Abstract:  Current research at Texas Tech University is focused on the development of a High-Power Pulsed Ring-Down Source (PRDS) Antenna Array. Previously, a Monte Carlo based analysis was conducted in order to predict the array performance based upon the estimated switching jitter between elements. This analysis showed good performance for jitter times between 0 to 2 periods of the ringing frequency. Therefore, for ringing frequencies up to 500 MHz, jitter times up to 4 nanoseconds can be tolerated. Subsequently, we have shown practical switching solutions capable of the sub-nanosecond switching performance needed for the frequencies of interest. Taking the analysis a step further, we introduce the uncertainty of the absolute position of each antenna element. To implement a randomly distributed array, where the position of elements is not fixed, a method of accurately resolving element positions relative to each other and the target location is required. The use of a variety of GPS technologies and techniques is explored as a method for position and timing resolution. The relative accuracy between elements and the absolute accuracy of each element is discussed. A Monte Carlo based analysis is conducted to predict array performance based upon GPS positional error, GPS timing error, and switch jitter.

[PDF]

+ Time-Resolved Spectral Investigations of Pulsed Atmospheric Dielectric Surface Flashover Discharges
  K. Frank, G. Laity, A. Neuber, G. Rogers, L. Hatfield, J. Dickens, M. Kristiansen, A. Fierro, "Time-Resolved Spectral Investigations of Pulsed Atmospheric Dielectric Surface Flashover Discharges," 63rd Gaseous Electronics Conference, October 4th - 8th, Paris, France, (2010).
Abstract:  In an attempt to identify the mechanisms leading to pulsed dielectric surface flashover in atmospheric conditions, a surface flashover event occurring on a magnesium fluoride (MgF$_{2})$ window was studied. The electrode configuration and the applied pulsed voltage level were chosen such that the generated electric field was symmetric with respect to the centerline between the electrodes. Sharpened stainless steel electrodes (estimated tip radius of 200$\mu $m) are attached to springs which press down onto the MgF$_{2}$ surface a distance of 8 mm apart. Diagnostics include time resolved emission spectroscopy in the VUV range and gated ICCD optical imaging of streamer progression during the first 30 nanoseconds of breakdown (with 3 nanosecond resolution) in the visible wavelength range. One important parameter on which the streamer formation and the subsequent breakdown strongly depends is the gas type and/or the gas composition. That is why the streamer formation was recorded for gated intervals from 3 to 50 ns in lab air, standard nitrogen, oxygen and SF$_{6}$. The results are compared to those ones in purified air, oxygen and nitrogen.

[PDF]

Publication Year:  2009
+ A 15 kA Linear Transformer Driver
  D. Matia, M. Giesselmann, A. Neuber, M. K. Kristiansen, "A 15 kA Linear Transformer Driver," Proceedings of the 2009 IEEE Pulsed Power Conference (PPC), pp. 926-929, Washington, DC, June 2009.
Abstract:  The design of a 15 kA linear transformer driver (LTD) is presented. The specific goal of this LTD was improved energy density over the 500 J compact Marx generator previously designed and built at Texas Tech's Pulsed Power lab. The design of an individual 50 joule, 30 kV stage is discussed. For successful operation of the LTD, multiple spark gaps have to be fired with low jitter. Possible approaches for the design of a compact, low jitter triggering circuit will be presented as well.

[PDF]

+ Development of a 40 stage distributed Energy Railgun
  Ryan Karhi, Michael Giesselmann, David Wetz, and Jeff Diehl, "Development of a 40 stage distributed Energy Railgun", Proceedings of the 2009 IEEE International Pulsed Power Conference, Washington, DC, June 29 - July 02, 2009, refereed Conference.
Abstract:  The development process pertaining to the design, fabrication, and testing of a 40-stage free-running arc synchronous distributed energy railgun is presented. Investigation of this type of system will determine the effectiveness of a distributed energy scheme to suppress the plasma restrike phenomenon and increase plasma armature railgun performance. Determined by a computer simulation, the proposed system will have a 1.0 cm ? 1.0 cm square bore cross section and a stage length of 15.24 cm producing a total rail length of 6 meters for 40 stages. A free-arc is utilized to relieve the financial burden of a large stored energy facility. A velocity of 8 km/s is desired to emulate conditions during a high altitude microsatellite launch. To achieve this velocity, pulsed power in conjunction with a low pressure (~ 10 Torr) air environment is required. The pulsed power supplies 15 kJ of energy to provide an armature current (~ 50 kA) for 1 millisecond. A real-time feedback control system will accurately release the stage energy upon arc arrival. Experimental data collected from a 7-stage prototype distributed system is discussed which will mimic the design and operation of the first 7 stages associated with the 40-stage railgun. The copper rail length is 1.2 m long with a 1 cm ? 1 cm square bore cross section and a 15.24 cm stage length. Each distributed energy stage contains a 750 ?F capacitor bank, a thyristor with an anti-parallel diode, and a driver board for triggering. The armature is formed using a plasma injector that is powered by a 40 kV Marx generator. Diagnostics for this examination include rail B-dot probes as well as independent Rogowski coils for each stage. Data collected from the rail B-dot probes will be used to measure the armature position and velocity as a function of time. There is no target velocity for this prototype; repeatable energy module operation, accurate stage triggering, and arc propagation toward the muzzle are the main areas focus. Outcom- es of these initial experimental results will aid the development of the 40-stage system.

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+ Electrical Conduction in Select Polymers under Shock Loading
  C. F. Lynn, A. A. Neuber, J. T. Krile, J. Dickens, M. Kristiansen, "Electrical Conduction in Select Polymers under Shock Loading," Proceedings of the 2009 IEEE Pulsed Power Conference (PPC), pp. 171-174, Washington, DC, June 2009.
Abstract:  It is known that polymers become conductive under shock loading, which can be critical to the operation of explosive driven high current/voltage devices. Hence, the propensity of several select polymers to conduct under shock loading was investigated. Four polymers, Nylon, Teflon, Polypropylene, and High Density Polyethylene, were tested under shock pressures up to ~22 GPa. Shock waves were generated with high explosives, and CTH, a hydrodynamic code developed at Sandia National Laboratories, was utilized to calculate pressure and temporal resolution of the shock waves. Time of arrival measurements of the shock waves were taken to correlate the hydrodynamic calculations with experimental results. A notable delay between shock front arrival and the onset of conduction is exhibited by each polymer. The delay tends to decrease with increasing pressure down to approximately 500 ns for HDPE at ~22 GPa under electric field strength of ~6.3 kV/cm. The data shows that some polymers exhibit more delay than others, thereby indicating better insulating properties under shock loading. Additionally, experiments revealed that the polymers conducted for a finite time on the microsecond time scale before recovering back to an insulating state. This recovery from a shock wave induced conducting state back to insulating state was investigated for a possible opening switch application.

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+ Energy Deposition Assessment and Electromagnetic Evaluation of Electroexplosive Devices in a Pulsed Power Environment
  J. Parson, J. Dickens, J. Walter, A. Neuber, "Energy Deposition Assessment and Electromagnetic Evaluation of Electroexplosive Devices in a Pulsed Power Environment," Proceedings of the 2009 IEEE Pulsed Power Conference (PPC), pp. 892-895, Washington, DC, June 2009.
Abstract:  This paper assesses critical activation limits of electroexplosive devices (EED), such as blasting caps, which have recently found more usage in pulsed power environments with high EMI background. These devices, EEDs, can be very sensitive to low levels of energy (7-8 mJ) which make them dangerous to unintended radiation produced by compact pulsed generators. Safe operation and use of these devices are paramount when in use near devices that produce pulsed electromagnetic interference. The scope of this paper is to provide an evaluation of activation characteristics for EEDs that include energy sensitivity tests, thermodynamic modeling, and electromagnetic compatibility from pulsed electromagnetic interference. Two methods of energy deposition into the bridgewire of the EED are used in the sensitivity tests. These methods include single and periodic pulses of current that represent the adiabatic and non-adiabatic heating of the bridgewire. The heating of the bridgewire is modeled by a solution to the heat equation using COMSOL¿ with physical geometries of the EED provided by the manufacturer.

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+ High Power Compact Capacitor Charger
  Michael G. Giesselmann, Travis T. Vollmer, "High Power Compact Capacitor Charger", Proceedings of the 2009 IEEE International Pulsed Power Conference, Washington, DC, June 29 - July 02, 2009, Lead author, main contributor, refereed Conference.
Abstract:  We are reporting on a new design for a compact high power Capacitor charger with a power output that far exceeds the peak power of previously reported designs. For this purpose we are evaluating parallel modular designs with separate inverters, transformers, & rectifiers and compare them with designs with a larger module size. For larger power implementations with a single inverter, transformer, & rectifier, the main challenge is the design of the inverter using parallel connected IGBT transistors and their current sharing. We are demonstrating an implementation were we are combining 2 H-Bridge inverters in parallel to feed the primary of a 100 kVA compact step-up transformer. Each H-Bridge is using current mode control to enforce current sharing. The oscillators in the current mode control IC's for each H-Bridge are synchronized for this parallel mode of operation. This topology could be expanded to more H-Bridges. In order to reduce the high-frequency impedance and the windings losses of the step-up transformer, litz wire is used for both the primary winding and the secondary windings.

[PDF]

+ Impact of DC Electric Fields on HPM Induced Surface Flashover
  M. Thomas, J. Foster, H. Krompholz, A. Neuber, "Impact of DC Electric Fields on HPM Induced Surface Flashover," 36th IEEE International Conference on Plasma Science, May 31st - June 5th, San Diego, CA, (2009)
Abstract:  Summary form only given. The introduction of a high voltage DC electrode into an experimental setup used for observing high power microwave surface flashover has shown to significantly vary the total delay time for this type of breakdown. The experiment utilizes an S-band magnetron operating at 2.85 GHz to produce a 4 MW, 3 mus pulse. A plasma switch mounted in a WR-284 waveguide reduces the 10-90% rise time of the pulse to ~50 ns, and it reflects the pulse towards a dielectric window to induce surface flashover. A wire electrode charged to plusmn20 kV is inserted into the center of the dielectric window and oriented perpendicularly to the major electric field component of the TE10 microwave mode. The DC field from the electrode influences charge carriers in the flashover region, forcing potential breakdown initiating charged particles away from or towards the surface, dependent on polarity and particle charge sign. Initial tests were conducted in pure N2 at a pressure of 125 torr. The low probability of negative ions (stable negative N2 ions do not exist) appearing in the volume simplifies the interpretation of the experimental results by allowing for the existence of primarily electrons and positively charged ions. A significant increase (~50%) in the average total delay time for the case of a positively charged electrode has been observed. An increase in the average statistical delay was also observed as well as a decrease in the presumed formative delay for both voltage polarities. The apparent electron production rate in N2 was estimated to be 2 e/mus and 8 e/mus under HPM pulse application in the case of positive and negative DC voltages, respectively. Results of further tests conducted in Argon and Krypton-85 in Argon balance are presented along with a statistical analysis of measured delay times.

[PDF]

+ Initial Results of Time-Resolved VUV Spectroscopy of Pulsed Dielectric Surface Flashover in Atmosphere
  G. Laity, K. Frank, G. Rogers, A. Neuber, J. Dickens, J.B. Moss, "Initial Results of Time-Resolved VUV Spectroscopy of Pulsed Dielectric Surface Flashover in Atmosphere," 51st Annual Meeting of the APS Division of Plasma Physics, November 2nd - 6th, Atlanta, GA, (2009).
Abstract:  Not Available
+ Integration of a Self-Contained Compact Seed Source and Trigger Set for Flux Compression Generators
  M. A. Elsayed, A. A. Neuber, M. Kristiansen, L. L. Altgilbers, "Integration of a Self-Contained Compact Seed Source and Trigger Set for Flux Compression Generators," Proceedings of the 2009 IEEE Pulsed Power Conference (PPC), pp. 297-300, Washington, DC, June 2009.
Abstract:  Two integral components that accompany an FCG in an explosively driven system is the prime power source and the trigger set. The objective of the prime power source or seed source is to provide the initial seed current/energy into the primary stage of an FCG. Another integral component in an FCG based pulsed power system is the trigger set. The trigger set is used to detonate an exploding bridge wire (EBW) which triggers the high explosives (HE's) in an FCG. This paper will discuss a recent design of a stand-alone apparatus that implements a self-contained (battery powered with full charge time less than 40 sec), single-use Compact Seed Source (CSS) using solid state components for the switching scheme along with a single-use Compact Trigger Set (CTS) that also implements a similar switching technique. The CSS and CTS stand-alone apparatus developed is a system (0.005-m3 volume and weighing 3.9 kg) capable of delivering over 360-J (~12 kA) into a 5.20-¿H FCG load and approximately 2-mJ (~600 A) into the EBW. Both the CSS and CTS have trigger energies of micro-Joules at the TTL triggering level.

[PDF]

+ Low Jitter Triggered Spark Gap with High Pressure Gas Mixtures and Kr85
  Y.J. Chen, J.C. Dickens, J.W. Walter, M. Kristiansen, "Low Jitter Triggered Spark Gap with High Pressure Gas Mixtures and Kr85," 36th IEEE International Conference on Plasma Science, May 31st - June 5th, San Diego, CA, (2009).
Abstract:  Summary form only given. A recent research effort at Texas Tech University on impulse antenna phased arrays has necessitated the need to develop a reliable high voltage, high repetition rate switch that will operate with ultra low jitter. An ideal jitter of a small fraction of the risetime is required to accurately synchronize the array to steer and preserve the risetime of the radiated pulse. A 50 Omega, 1 nF pulse forming line is charged to 50 kV and provides the low inductance voltage source to test the different gases. Triggering is provided by a solid state opening switch voltage source that supplies ~80 kV, 10 ns risetime pulses at a rep rate up to 100 Hz in burst mode. A hermetically sealed spark gap with a Kel-F lining is used to house the switch and high pressure gas. Previously, the system was successfully tested with 50 kV, 100 Hz switch operations. Gases tested include, dry air, H2, N2, and SF6, as well as H2-N2, and N2-SF6 gas mixtures. A discussion on switch operation time and switch gas temperature vs. jitter will be included in this paper. This paper will also discuss in detail the effects on switch jitter when different concentrations of Kr85 gas are introduced.

[PDF]

+ Power Conditioning Optimization for a Flux Compression Generator Using a Non-Explosive Testing System
  C. B. Davis, A. Young, A. A. Neuber, J. C. Dickens, M. Kristiansen, "Power Conditioning Optimization for a Flux Compression Generator Using a Non-Explosive Testing System," Proceedings of the 2009 IEEE Pulsed Power Conference (PPC), pp. 951-955, Washington, DC, June 2009
Abstract:  Not Available
+ Prediction of Compact Explosively-Driven Ferroelectric Generator Performance
  D. W. Bolyard, A. Neuber, J. Krile, J. Dickens, M. Kristiansen, "Prediction of Compact Explosively-Driven Ferroelectric Generator Performance," Proceedings of the 2009 IEEE Pulsed Power Conference (PPC), pp.167-170, Washington, DC, June 2009
Abstract:  Explosively-driven ferroelectric generators are attractive as potential prime energy sources for one-time use pulsed power systems. While the output voltages of small ferroelectric discs have been shown to be on the order of the theoretical maximum values, scaling the ferroelectric to larger thicknesses has proven less successful. The primary limiting factor is how much of the ferroelectric material is compressed simultaneously. This is difficult to control for thicker ferroelectric discs or stacks of discs due to pressure pulse attenuation in the material and rarefaction waves shortening the pressure pulse. A hydrodynamic code system is utilized to calculate the temporally and spatially resolved pressure. The calculated pressure values are converted into voltage produced by the ferroelectric through an algorithm based on an empirical polarization-pressure hysteresis curve. The validity of the algorithm has been verified for PZT EC-64 with experimental data from a flyer-plate experiment reported in literature and our own experiments with the shock wave from the explosives more directly applied to the ferroelectric. Both calculations and experiments produced normalized output voltages, ranging from 1.4 to 3.4 kV/mm for 2.54 cm diameter discs. We will discuss how this pressure to voltage algorithm along with pressure simulations aided in the scaling of the amount of ferroelectric material in a generator, as well as in the design of new driver elements with the goal to increase the peak output voltage of a generator while keeping the generator compact. The calculated voltage output results are compared with experimental data of explosively-driven ferroelectric generators.

[PDF]

+ Stand-Alone, FCG-Driven High Power Microwave System
  A. Young, M. Elsayed, J. Walter, A. Neuber, J. Dickens, M. Kristiansen, L. Altgilbers, "Stand-Alone, FCG-Driven High Power Microwave System," Proceedings of the 2009 IEEE Pulsed Power Conference (PPC), pp. 292-296, Washington, DC, June 2009.
Abstract:  An explosively driven High Power Microwave (HPM) source has been developed that is based on the use of a Flux Compression Generator (FCG) as the primary driver. Four main components comprise the HPM system, and include a capacitor-based seed energy source, a dual-staged FCG, a power conditioning unit and an HPM diode (reflex-triode vircator). Volume constraints dictate that the entire system must fit within a tube having a 15 cm diameter, and a length no longer than 1.5 m. Additional design restrictions call for the entire system to be stand-alone (free from any external power sources). Presented here are the details of HPM system, with a description of each subcomponent and its role in the generation of HPM Waveforms will be shown which illustrate the development of power as it commutates through each stage of the system, as well as power radiated from the diode. Analysis and comparisons will be offered that will demonstrate the advantages of an explosively driven HPM system over more conventional pulsed power devices.

[PDF]

+ The Influence of a DC Electric Field on High Power Microwave Window Flashover in Air and N2 Environments
  J. Foster, M. Thomas, H. Krompholz, A. Neuber, "The Influence of a DC Electric Field on High Power Microwave Window Flashover in Air and N2 Environments," Proceedings of the 2009 IEEE Pulsed Power Conference (PPC), pp. 480-483, Washington, DC, June 2009.
Abstract:  Observed delay times for high power microwave surface flashover are influenced significantly by the presence of a DC electric field. The experimental setup to investigate theses influences is comprised of an S-band magnetron operating at 2.85 GHz with a pulse rise time shortening switch assembly that produces a 50 ns rise time at a ~ 2.5 MW power level. A wire electrode charged to ±20 kV is inserted into the dielectric interface perpendicular to the electric field of the TE10 mode to provide a DC electric field in the flashover region. Tests have been conducted in pure N2 at 125 torr in order to provide an environment composed of primarily electrons and positive ions. The average measured delay of window flashover with a DC field pointing into the dielectric has been observed to increase by ~50%. Additionally, effective emission rates of seed electrons initiating breakdown have shown a decrease from 14 e/¿s to 2 e/¿s, indicating the removal of charged species from the high microwave field region due to charge drift in the applied DC field. An overview of the experimental setup is given along with a statistical analysis of delay times measured in Air as well as N2. The open question of where seed electrons originate from and the quantification of the primary processes involved will be addressed.

[PDF]

+ Use of Radiation Sources to Provide Seed Electrons in High Power Microwave Surface Flashover
  M. Thomas, J. Foster, H. Krompholz, A. Neuber, "Use of Radiation Sources to Provide Seed Electrons in High Power Microwave Surface Flashover," Proceedings of the 2009 IEEE Pulsed Power Conference (PPC), pp. 124-128, Washington, DC, June 2009.
Abstract:  Delay times of high power microwave surface flashover are affected by radiation illuminating the dielectric. A controlled environment of pure Argon at a range of low pressures as compared to normal atmospheric pressure was used with 2 mW/cm2 UV-radiation illuminating the test window. Argon was chosen due to its relatively small number of processes involved such as inelastic electron collisions and due to the well-known cross-sections for these processes. Delay times in the presence of UV are significantly shorter than without UV illumination. The initial electron density contribution due the UV source is very roughly estimated to be ~106 cm-3. A small admixture of radioactive krypton-85 showed only marginal changes in the observed delay times, likely due to an insufficient concentration of Kr-85 producing ionization events only every few microseconds and the high energy distribution associated with the emitted electrons. A detailed discussion of experimental breakdown delay data, along with theoretical expectations and discussion of the statistically dependent mechanisms and analysis, will be given. The ultimate goal is to develop a model for HPM window breakdown in a UV environment, to describe the role of discharge initiating electrons, and to quantify breakdown at high altitudes.

[PDF]

+ Vacuum Ultraviolet Spectroscopy of Dielectric Surface Flashover at Atmospheric Pressure
  G. Laity, K. Frank, G. Rogers, M. Kristiansen, J. Dickens, A. Neuber, T. Schramm, "Vacuum Ultraviolet Spectroscopy of Dielectric Surface Flashover at Atmospheric Pressure," 36th International Conference on Plasma Science, May 31st - June 5th, San Diego, CA, (2009).
Abstract:  Summary form only given. Spectroscopic measurements in the vacuum ultraviolet (VUV) regime are difficult to make due to extremely large absorption of VUV radiation in most materials. This paper describes an experimental setup designed for studying the optical emission during pulsed surface flashover for the wavelength range between 115 nm to 300 nm at atmospheric pressures. A vacuum monochromator VM 505 from Acton Research Corporation was used as the spectrograph. For VUV transmission down to 115 nm the light emitted by surface flashover across an MgF2 window (front side of window in air, backside in vacuum) was focused by an MgF2 lens onto the entrance slit of the spectrograph. A quartz window with sodium salicylate coating exposed to the spectrograph's vacuum was placed in the exit focal plane of the collimating mirror of the spectrograph. This fluorescent coating down-converts the VUV light to longer wavelengths that were recorded with an Andor DH520 series ICCD camera in combination with a Nikon 105 mm lens. Spectra were measured at atmospheric pressure with a flashover spark length of about 9 mm and DC excitation with a capacitance of 4.1 nF. Emission spectra were measured from 300 nm down to 130 nm. In parallel, theoretical spectra were calculated primarily for the identification of radiating species and their temperature. Utilizing the NIST Atomic Spectra Database (ASD) data a library of temperature dependent optical emission spectra was generated with SpectraPlot, a spectral software suite developed at TTU. VUV spectral lines of nitrogen, carbon, magnesium and silicon were identified. In pure nitrogen, for instance, the nitrogen I double line at 174.3 nm and 174.5 nm is clearly visible in the spectrum along with a strong double line at 279.6 nm and 280.4 nm, which is emitted by Magnesium II, eroded from the surface exposed to flashover. Spectra were measured in ambient air, pure nitrogen, and argon. An experiment upgrade is currently u- nderway, increasing the VUV sensitivity of the setup. The measured spectra will be discussed in relation to the physics of surface flashover and volume breakdown at atmospheric pressure.

[PDF]

+ VUV Emission from Dielectric Surface Flashover at Atmospheric Pressure
  T. G. Rogers, A. Neuber, G. Laity, K. Frank, J. Dickens, T. Schramm, "VUV Emission from Dielectric Surface Flashover at Atmospheric Pressure," Proceedings of the 2009 IEEE Pulsed Power Conference (PPC), pp. 855-859, Washington, DC, June 2009.
Abstract:  There is a growing interest in the physics of surface flashover between the interface of atmosphere and vacuum in some high-power systems. More specifically, the quantitative role of vacuum ultraviolet (VUV) radiation for the photoionization leading to a streamer development during the initial stages of a breakdown is unknown. This paper describes an experimental setup used to measure the VUV radiation emitted from atmospheric flashover as well as time-resolved imaging of the flashover event. A pulser providing the voltage to the gap was designed with special considerations in mind, including long lifetime, low noise, and high reproducibility. This enabled the study of the flashover in various background gases with an emphasis on spectroscopic measurements. The calculated spectra are compared with the measured spectra, and it is found that atomic oxygen and nitrogen are responsible for most of the VUV production in an air breakdown at atmospheric pressure in the wavelength range of 115–180 nm. Time-resolved spectroscopy reveals that the VUV radiation is emitted during the initial stages while the streamers are developing.

[PDF]

Publication Year:  2008
+ A 50 kV, 100 Hz Low Jitter Triggered Spark Gap with High Pressure Gas Mixtures
  Chen, Yeong-Jer; Mankowski, John J.; Dickens, James C.; Walter, John; Kristiansen, Magne; A 50 kV, 100 Hz Low Jitter Triggered Spark Gap with High Pressure Gas Mixtures; IEEE International Power Modulators and High Voltage Conference, Proceedings of the 2008; 27-31 May 2008 Page(s):197 - 200; Digital Object Identifier 10.1109/IPMC.2008.4743614
Abstract:  Recent research efforts at Texas Tech University on impulse antenna phased array has necessitated the need to develop a reliable high voltage, high repetition rate switch that will operate with ultra low jitter. An ideal jitter of a small fraction of the risetime is required to accurately synchronize the array to steer and preserve the risetime of the radiated pulse. In (Y. Chen et al., 2007), we showed the initial test system with sub-ns results for operations in different gases and gas mixtures. This paper presents the impact gases and gas mixtures have on switch performance which includes recovery rate and in particular jitter. A 50 Omega, 1 nF pulse forming line is charged to 50 kV and provides the low inductance voltage source to test the different gases. Triggering is provided by a solid state opening switch voltage source that supplies ~150 kV, 10 ns risetime pulses at a rep rate up to 100 Hz in burst mode. A hermetically sealed spark gap with a Kel-F lining is used to house the switch and high pressure gas. This paper discusses in detail 50 k, 100 Hz switch operations with different gases. Gases tested include, dry Air, H2, N2, and SF6, as well as H2-N2, and N2-SF6 gas mixtures. Switch jitter as a result of triggering conditions is discussed, also including a comprehensive evaluation of jitter as a function of formative delay in the various gases.

[PDF]

+ A Compact, Self-Contained High Power Microwave Source Based on a Reflex-Triode Vircator and Explosively Driven Pulsed Power
  A. Young, T. Holt, M. Elsayed, J. Walter, J. Dickens, A. Neuber, M. Kristiansen, L.L. Altgilbers, and A.H. Stults, A Compact, Self-Contained High Power Microwave Source Based on a Reflex-Triode Vircator and Explosively Driven Pulsed Power, to be published in the Proceedings of the 2008 IEEE International Power Modulator Conference Las Vegas, Nevada, USA, May 27-31, 2008.
Abstract:  Single-shot high power microwave (HPM) systems are of particular interest in the defense industry for applications such as electronic warfare. Virtual cathode oscillators (vircators) are manufactured from relatively simple and inexpensive components, which make them ideal candidates in single-shot systems. The flux compression generator (FCG) is an attractive driver for these systems due to its potential for high energy amplification and inherent single-shot nature. A self-contained (battery operated prime power), compact (0.038 m3), FCG-based power delivery system has been developed that is capable of delivering gigawatts of power to a vircator. Experiments were conducted with the delivery system connected to a resistive dummy load and then to a reflex-triode vircator. In order to optimize the performance of the vircator when driven by the power delivery system, a second experimental setup was constructed using a Marx-generator based system operating at similar voltages and rise-times. Performance measures of the delivery system when discharged into a resistive load will be presented, as well as vircator output power levels and waveforms from both experimental setups.

[PDF]

+ Analysis of Mesoband Single Element Pulsed Ring-Down Antennas for Implementation in Phased Array Systems
  Belt, D.; Mankowski, J.; Walter, J.; Dickens, J.; Kristiansen, M.; IEEE International Power Modulators and High Voltage Conference, Proceedings of the 2008 27-31 May 2008 Page(s):152 - 155 Digital Object Identifier 10.1109/IPMC.2008.4743602
Abstract:  In recent years, the pulsed ring-down antenna has become of great interest due to its compact size and high power on target potential. Since these systems are fairly new in study, it is often difficult to predict the overall performance without experimental evaluation. A pulsed ring-down antenna operates by charging the single element antenna with a high potential source and then closing a switch to develop transient wave reflections on the antenna, typical CW case analysis does not apply. For this reason, we have constructed a simulation model that allows us to predict the transient behavior of the structure. By utilizing the Comsol RF module transient analysis functions, we are able to characterize various parameters of different antennas, beginning with a dipole pulsed ring-down antenna operating around the 100 MHz range. After examining the simulated results against the experimental results for accuracy, we then moved to more complicated mesoband antenna structures. The simulation model developed within the COMSOL RF module allows us to examine various influential factors such as material losses, transient switching effects, structure capacitance, switch capacitance, and initial charging losses. With this, we are able to examine methods to improve the results in the far field such as capacitive spark gap loading and other capacitive storage methods. Utilizing the pulsed ring-down antenna model, we are able to give a better characterization of mesoband pulsed ring-down structures for implementation into a specific or multi-purpose phased array system.

[PDF]

+ Capacitor Evaluation For Compact HV Pulse Generation
  E. J. Matthews, A. A. Neuber, M. Kristiansen, Capacitor Evaluation For Compact HV Pulse Generation, to be published in the Proceedings of the 2008 IEEE International Power Modulator Conference Las Vegas, Nevada, USA, May 27-31, 2008.
Abstract:  The size of compact pulsed power generators capable of producing pulses with ~100 ns duration at Gigawatt power levels is primarily determined by the specific energy density of the utilized energy storage medium. Capacitors capable of delivering large pulsed currents at several 10 kV voltage levels have been most frequently used as the energy storage medium for portable pulse generators. To increase the specific energy density of the pulsed power generator, the capacitors are often voltage overstressed at the cost of capacitor life. However, rapid charging (milliseconds) of the capacitor immediately followed by discharging alleviates somewhat of the lifetime problem. For repetitive operation of the pulsed power generator, the charging/discharging energy loss is the more important parameter. The energy, WC, needed to charge a capacitor to a set voltage is measured along with the energy released, WR, by the capacitor under conditions corresponding to a compact Marx generator operating with ~10 Hz rep-rate into a ~20 Ohm load. For the tested capacitors with Mica as dielectric, the capacitor efficiency, eta, i.e. the ratio between WR and WC, is roughly equal to 97% and largely independent of the charging time. Also tested ceramic capacitors revealed an efficiency of ~90% for fast charging and an efficiency of ~94% for slower charging (from ~2 to 35 mus time constant).

[PDF]

+ Compact High Power Microwave Generation
  Neuber, A. Young, M. Elsayed, J. Dickens, M. Giesselmann, M. Kristiansen, L. Altgilbers, Compact High Power Microwave Generation, Proceedings of the 2008 Army Science Conference, Orlando Florida, December 1-4, 2008. Presenter, P3E team contribution, paper was invited by L. Altgilbers.
Abstract:  Not Available
+ Compact HV-Capacitor Charger
  Giesselmann, Michael; Vollmer, Travis; Lara, Matt; Mayes, Jon, Compact HV-Capacitor Charger, Proceedings of the 2008 IEEE International Power Modulator Conference, Las Vegas, Nevada, May 27-31, 2008, Page(s):238 – 241. Lead author, main contributor, refereed Conference.
Abstract:  We are reporting on a compact high power charger which is integrated into compact Marx generators for rep. rated high power microwave generators and other pulsed power applications. The charger uses rectified AC mains input voltages of 120 V single phase or 208 V three phase and produces output voltages of up to ten's of kV with HV output power levels of 10 kW. The rep. rate capability is up to 100 Hz. Major advancements over previous designs are current mode control of the main inverter and improved voltage feedback control.

[PDF]

+ Compact HV-DC Power Supply
  Michael Giesselmann, Travis Vollmer, Ryan Edwards, "Compact HV-DC Power Supply", Proceedings of the 2008 IEEE Power Modulator Conference, May 27-30, 2008, Las Vegas, NV, May 30, 2008
Abstract:  We are reporting on a compact High Voltage (HV) power supply that can be used in the mobile or airborne generation of High Power Microwave generators. The charger uses rectified AC mains input voltages of 480V three phase and produces output voltages of more than 55 kV with HV output power levels of 100's of kW continuously. Major advancements over a previous design [1] are the design of the secondary winding of the HV nano-crystalline transformer, the control of the primary inverter and the thermal management and diagnostic of the HV-DC rectifier.

[PDF]

+ Compact Silicon Carbide Switch For High Voltage Operation
  James, C.; Hettler, C.; Dickens, J.; Neuber, A.; Compact Silicon Carbide Switch For High Voltage Operation; IEEE International Power Modulators and High Voltage Conference, Proceedings of the 2008 27-31 May 2008 Page(s):17 - 20 Digital Object Identifier 10.1109/IPMC.2008.4743565
Abstract:  Vanadium compensated, 6H silicon carbide (SiC) is investigated as a compact, high-power, linear-mode photoconductive semiconductor switch (PCSS) material. SiC is an attractive material due to its high resistivity, high electrical breakdown strength, and long recombination times compared to other photoconductive materials. The PCSS is designed for fast-rise time, low-jitter (sub-nanosecond) operation in a matched 50 mu test bed. Ohmic contacts were applied by physical vapor deposition and initial test utilized an external Nd:YAG laser trigger source. Analysis of the optical properties of Va-compensated SiC and of switch conduction resistance are presented and performance of contact material is discussed.

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+ Comparison of HFCG and Compact Marx for Driving a High Power Microwave Load
  A. Neuber, A. Young, M. Elsayed, J. Walter, J. Dickens, M. Giesselmann, M. Kristiansen,and L.L. Altgilbers, Comparison of HFCG and Compact Marx for Driving a High Power Microwave Load, 12th IEE Conference on Megagauss Magnetic Field Generation, (Novosibirsk, Russia), July 2008, to be published.
Abstract:  Not Available
+ Energy Deposition and Electromagnetic Compatibility Assessment of Electroexplosive Devices
  Parson, J.; Dickens, J.; Walter, J.; Neuber, A.; IEEE International Power Modulators and High Voltage Conference, Proceedings of the 2008 27-31 May 2008 Page(s):439 - 442 Digital Object Identifier 10.1109/IPMC.2008.4743684
Abstract:  This paper assesses the critical activation energy required to set off electroexplosive devices (EED) at constant joule heating and rates of joule heating. Safe operation and use of these devices are of great concern in and around pulsed electromagnetic interference. Sensitivity characterization of EEDs include firing sensitivity plots, thermodynamic modeling and electromagnetic interference. Activation energy evaluation of single and periodic rectangular pulses are included to represent adiabatic and non-adiabatic bridge wire heating of the EED. The scope of this paper is to provide a short overview of sensitivity, thermodynamic, and electromagnetic compatibility of EEDs. The results provide crucial information in evaluating energy induced by pulsed electromagnetic fields of compact pulse generators.

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+ High-Current Compact FCG Seed Source Implementing Solid State Switching
  M. Elsayed, T. Holt, A. Young, A. Neuber, J. Dickens, M. Kristiansen, L.L. Altgilbers, and A.H. Stults, High-Current Compact FCG Seed Source Implementing Solid State Switching, to be published in the Proceedings of the 2008 IEEE International Power Modulator Conference Las Vegas, Nevada, USA, May 27-31, 2008.
Abstract:  Flux Compression Generators (FCGs) are some of the most attractive sources of single-use compact pulsed power available today due to their high energy density output and mobility. Driving FCGs requires some seed energy, which is typically provided by applying a high seed current, usually in the kilo-Ampere range for mid-sized helical FCGs. This initial current is supplied by a high-current seed source that is capable of driving an inductive load. High-current seed sources have typically been comprised of discharging large capacitors using spark-gaps and over-voltage triggering mechanisms to provide the prime power for FCGs. This paper will discuss a recent design of a self-contained (battery powered with full charge time less than 35 sec), single-use Compact Seed Source (CSS) using solid state components for the switching scheme developed at the Center for Pulsed Power and Power Electronics at Texas Tech University. The CSS developed is a system (0.007-m3 volume and weighing 13 lbs) capable of delivering over 250-J (~10 kA) into a 6-muH load with a trigger energy of micro-Joules at the TTL triggering level. The newly designed solid-state switching scheme of the CSS incorporates off-the-shelf high-voltage semiconductor components that minimize system cost and size as necessary for a single-use application. An in-depth and detailed evaluation of the CSS is presented primarily focusing on the switching mechanics and experimental characterization of the solid state components used in the system.

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+ Jitter and recovery rate of a 50 kV, 100 Hz triggered spark gap with high pressure gas mixtures
  Yeong-Jer Chen; Mankowski, J.J.; Walter, J.W.; Dickens, J.C.; Jitter and recovery rate of a 50 kV, 100 Hz triggered spark gap with high pressure gas mixtures; Plasma Science, 2008. ICOPS 2008. IEEE 35th International Conference on 15-19 June 2008 Page(s):1 - 1 Digital Object Identifier 10.1109/PLASMA.2008.4590809
Abstract:  Summary form only given.Recent attention to impulse antenna phased array has necessitated the need to develop a reliable high voltage, high repetition rate switch that will operate with ultra low jitter. An ideal jitter of a small fraction of the rise time is required to accurately synchronize the array to steer and preserve the rise time of the radiated pulse. This paper presents the impact gases and gas mixtures have on switch performance which includes recovery rate and in particular, jitter. A 50 Omega, 1 nF pulse forming line is charged to 50 kV and provides the low inductance voltage source. Triggering is provided by an SOS voltage source that supplies >100 kV, 10 ns rise-time pulses at a rep rate up to 1 kHz in burst mode. A hermetically sealed spark gap with a Kel-F lining is used to house the switch and high pressure gas. The system includes a gas mixing chamber that can mix various gases up to 2000 psi. Gases tested include dry air, H2, N2, and SF6. Initial testing with 30 kV, 10 Hz switch operations have shown reliable sub-ns jitter times with pure gases including dry air, H2, N2, and with H2-N2, and N2-SF6 gas mixtures. The system was then modified for 50 kV, 100 Hz operations with no recovery issues. Jitter data for pure gases, H2-N2, N2-SF6, and various Kr85 gas mixtures at the 50 kV, 100 Hz operation is also documented and compared in this paper.

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+ Opening Switch Utilizing Stress Induced Conduction In PMMA
  C. Lynn, A. Neuber, J. Dickens, J. Krile, Opening Switch Utilizing Stress Induced Conduction In PMMA, presented at the 2008 IEEE International Power Modulator Conference Las Vegas, Nevada, USA, May 27-31, 2008.
Abstract:  It is known that polymethylmethacrylate, PMMA, becomes conductive under shock loading. To develop an opening switch utilizing shock induced conduction, the reversibility of this process must be studied. It is suggested in literature that changes in electrical properties begin at pressures as low a ~2 GPa. Applying the minimum pressure necessary for conduction is desirable in order to maximize the reversibility by limiting compression heating of the material. CTH, a hydrodynamic code written at Sandia National Laboratory, was used to design various drivers that deliver pressures in the range of ~2 GPa to ~6 GPa to the PMMA. By utilizing the switch to trigger an RC discharge, the resistance and on-time of the switch was characterized. Experiments have shown conduction durations on the order of ~4 mus. The switch was then placed into a capacitive driven inductive energy storage circuit, IES, to determine the polymer's ability to recover. This paper will present experimental data, CTH simulation results, and discuss the attained switching characteristics under varying shock pressure profiles.

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+ Particle Simulation of Ultrafast Closing Switch at Sub-Atmospheric Pressures
  Jordan Chaparro, Hermann Krompholz, Andreas Neuber, Lynn Hatfield, Particle Simulation of Ultrafast Closing Switch at Sub-Atmospheric Pressures, IEEE International Power Modulator Conference, Las Vegas, NV, May 27-31, 2008
Abstract:  Previous research at Texas Tech University has been conducted on the physics governing highly over-voltaged gas breakdown resulting from ultrafast applied voltage pulses with risetimes less than 200 ps and durations less than 400 ps. Experimental results have shown that the breakdown characteristics of such events significantly differ from those observed in standard gas breakdown and a complete understanding of the physics behind ultrafast discharges is far from being clear. As a companion to experimental work, a numerical model is an attractive means of discerning more about the underlying physics behind such events. In this paper, a relativistic, Particle in cell model utilizing Monte-Carlo calculations is discussed as a way to directly simulate the experimental conditions, with similar geometry, background gas, and pulse characteristics. Diagnostic output from the simulation includes space-charge development over time, field and particle energy distributions, and particle number growth rates and spatial distributions. An overview of the structure and formulation behind the simulation code is given followed by a comparison of output data to experimental results. Specific points of interest for comparison include formative and statistical delay times, examination of inhomogeneous ionization regions in the discharge, and the behavior of high-energy particles in the runaway state.

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+ Scaling and Improvement of Compact Explosively-Driven Ferroelectric Generators,
  D. Bolyard, A. Neuber, J. Krile, J. Walter, J. Dickens, and M. Kristiansen, Scaling and Improvement of Compact Explosively-Driven Ferroelectric Generators, to be published in the Proceedings of the 2008 IEEE International Power Modulator Conference Las Vegas, Nevada, USA, May 27-31, 2008.
Abstract:  Explosively-driven ferroelectric generators are capable of producing single-shot voltage pulses of more than 100 kV, while requiring no seed electrical source, being very compact, and shelf stable. Problems with ferroelectric generators are the low energy output, high dielectric constant of the ferroelectric material, low surface flashover voltage, inconsistent ferroelectric material quality, and uneven or excessive shockwave compression. Initial generator voltage waveforms show that breakdown occurred towards the end of the generator operation time. Several designs and methods have been tested and implemented to prevent surface flashover with varying results. The ferroelectric discs used for the generators were 0.4 inch thick, 1 inch diameter EC-64 PZT ceramic discs. Several six-disc generators were built and tested with resulting open-circuit voltage pulses of 80-140 kV with a FWHM of 2-4 mus. Further improvements to the generators have been designed to prevent surface flashover, improve the explosive driver element and propagating shockwave, as well as increasing the number of discs per generator. Measured output waveforms into varying loads including direct driven antennas will be shown and discussed.

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+ Shock Wave Simulation of Ferrite-Filled Coaxial Nonlinear Transmission Lines
  Sullivan, W.; Dickens, J.; Kristiansen, M.; Shock Wave Simulation of Ferrite-Filled Coaxial Nonlinear Transmission Lines; IEEE International Power Modulators and High Voltage Conference, Proceedings of the 2008 27-31 May 2008 Page(s):517 - 520 Digital Object Identifier 10.1109/IPMC.2008.4743706
Abstract:  Ferrite-filled coaxial shock lines have recently been used to significantly decrease the rise time of a high voltage pulse. This decrease can be enhanced by initially axially biasing the ferrite material with an applied external magnetic field, allowing for a faster transition from the unsaturated to the saturated state. The simulation of the ferrite material's operation, including saturation, is discussed as well as the simulation of coaxial nonlinear transmission lines. The project explores the rise time changes with variations of magnetic bias, ferrite geometry, input signal characteristics, and transmission line characteristics. Simulated waveforms are discussed for a nickel-zinc ferrite-filled coaxial line. The pulse steepening effect observed in electromagnetic shock lines occurs primarily because of an increase in phase velocity for points higher on the waveform due to the saturation of the ferrite material. An incident pulse of high enough amplitude will drive the ferrite material into saturation, decreasing the relative permeability to one. This saturation front propagates through the ferrite material in the direction of the incident wave until the entire material is saturated, producing a sub-nanosecond rise time pulse. The shock line is designed for a saturated impedance of 50 Ohms to couple easily into existing systems. Pulsed operation of up to low kilohertz repetition is desired and being explored. Applications of electromagnetic shock lines include laser triggering and ultra-wideband radar generation, as well as others.

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+ Short Rise Time High Power Microwave Induced Surface Flashover At Atmospheric Pressures
  J. Foster, G. Edmiston, J. Krile, A. Neuber, and H. Krompholz, Short Rise Time High Power Microwave Induced Surface Flashover At Atmospheric Pressures, to be published in the Proceedings of the 2008 IEEE International Power Modulator Conference Las Vegas, Nevada, USA, May 27-31, 2008.
Abstract:  High power microwave transmission is ultimately limited by window flashover at the vacuum-air dielectric boundary. While surface flashover in the presence of a vacuum has been studied in some detail, the mechanisms associated with flashover in an atmospheric environment need further investigation. For an aircraft based high power microwave system, atmospheric pressures ranging from 760 torr (sea level) to 90 torr (50,000 ft.) are of principal concern. The experimental setup uses a 2.85 GHz, 3 mus microwave pulse with a 10 to 90% rise time of approximately 600 ns from a magnetron capable of producing 5 MW. The slow rise time of the microwave pulse is sharply reduced by using a waveguide spark gap switch used for fast microwave reflection and a high power four port circulator [6]. This reflected pulse has a reduced rise time on the order of 50 ns. The shorter rise time produces a more ideal step waveform that can be more easily compared with theoretical perfect square pulse excitation. Past investigations showed that the delay time for breakdown in air increases with pressure as is expected from the right hand side of the Paschen curve as long as the electron collision frequency is much larger than the microwave frequency. Surface flashover experiments have produced similar results. At a pressure of 155 torr, for instance, the breakdown electric field strength is 6 kV/cm (power density 0.08 MW/cm2) and the overall delay time from HPM pulse application to reaching critical breakdown plasma density is 600 ns. An overview of the experimental setup is given along with a discussion of breakdown delay times as a function of pressure as well as an investigation of surface flashover in the presence of external UV (ultraviolet) illumination.

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+ Statistical and Formative Delay Times for Sub-Nanosecond Breakdown at Sub-Atmospheric Pressure
  Jordan Chaparro, Lynn Hatfield, Hermann Krompholz, Andreas Neuber, Statistical and Formative Delay Times for Sub-Nanosecond Breakdown at Sub-Atmospheric Pressure, IEEE International Power Modulator Conference, Las Vegas, NV, May 27-31, 2008
Abstract:  For subnanosecond switching, physical phenomena as well as basic breakdown data, such as delay times and breakdown voltages, are of interest. With a RADAN Pulser as source for voltage pulses with up to 180 kV amplitude and risetimes at a test gap of 180 ps, we investigate statistical and formative delays for argon and dry air at sub-atmospheric pressure, for gap widths of 1 and 11 mm. Formative times have minima between 50 and 200 torr, and range from 70 ps at 1.5 MV/cm to 200 ps at 50 kV/cm. For this range of electric fields, this dependence on pressure and applied field can be explained by the behavior of ionization coefficient and electron drift velocity for homogeneous discharges. For higher fields exhibiting a narrow ionization zone in cathode vicinity with pronounced electron runaway conditions, the experimental data agree with results of Monte-Carlo simulations. Statistical delays are about the same as formative delays at fields of 50 kV/cm, and are reduced with increasing field amplitude to less than 50 ps at 1.5 MV/cm. It appears that field emission is the major source for starting electrons, influencing the statistical delay time near the field emission threshold only.

[PDF]

+ Statistics of High Power Microwave Induced Window Flashover
  A. Neuber, G. Edmiston, J. Krile, J. Foster, H. Krompholz, Statistics of High Power Microwave Induced Window Flashover, presented at the 35th IEEE International Conference on Plasma Science, June 15 - 19, 2008, Karlsruhe, Germany
Abstract:  ummary form only given as follows. For flashover in air, nitrogen, and SF6, we have previously shown that the delay time between microwave pulse application and breakdown increases with pressure in the regime where the elastic electron collision frequency is larger than the microwave frequency (roughly >10 torr for 2.85 GHz microwave frequency), which also coincides with conditions found at the right hand side of the Paschen curve. The specific window flashover geometry was carefully chosen to avoid local field enhancement. That is, no metallic parts are exposed to high fields. Hence, only the window surface itself, the gas, and interaction processes between surface and volume contribute to flashover. A Monte Carlo based electron motion code developed for the flashover conditions predicts formative flashover delay times reasonably well in the pressure regime between 100 to 600 torr (10,000 Pa to 80,000 Pa). However, the statistical delay time, that is the time interval required for the initiatory electron(s) to appear, is unaccounted for in the code. Further computational efforts investigating seed electron production via collisional detachment from, for instance, negative ions in the gas have shown that while effective at unipolar fields, collisional detachment is unlikely to contribute to the production of seed electrons at higher microwave frequencies above several GHz. Experiments show that illuminating the surface with light/photons (180 nm < lambda < 350 nm) reduces the observed statistical delay considerably indicating the importance of seed electron production from the surface. This paper will discuss the key processes of high power microwave surface flashover and present experimental flashover data along with continued investigation into the statistics of possible seed electron sources, including trace contaminates present in the gas or on the dielectric surface.

[PDF]

+ Window Flashover Initiation Under Pulsed Microwave Excitation
  J. Krile, G. Edmiston, J. Dickens, H. Krompholz, and A. Neuber, Window Flashover Initiation Under Pulsed Microwave Excitation, to be published in the Proceedings of the 2008 IEEE International Power Modulator Conference Las Vegas, Nevada, USA, May 27-31, 2008.
Abstract:  Surface flashover development at the output window of high power microwave (HPM) systems presents a major limitation to the power densities and pulse lengths transmitted through these interfaces. As a result, developing a physical model accurate in predicting surface flashover initiation is of prime interest. A Monte-Carlo type electron motion simulation has been developed to estimate the delay time from initial electron to flashover. Although this approach has shown reasonable agreement with experimental results, the process yielding the initial seed electron(s) was neglected in the model, primarily due to the lack of quantitative and qualitative information on seed electron production. For instance, computational efforts investigating seed electron production via collisional detachment from negative oxygen ions have shown that while effective at DC, the collisional detachment model cannot remain a likely contributor of electrons at high frequencies (Gt ~5 GHz). The key parameters impacting high power microwave surface flashover will be discussed and presented along with continued investigation into the statistics of possible seed electron sources, including trace contaminates present in the gas or on the dielectric surface.

[PDF]

Publication Year:  2007
+ Characterization of a High Power Nanocrystalline Transformer
  Ryan C. Edwards and Michael G. Giesselmann, Characterization of a High Power Nanocrystalline Transformer, Proceedings of the 2007 IEEE Pulsed Power & Plasma Science Conference, Albuquerque, NM, June 17-22, 2007 (A).
Abstract:  Not Available
+ Dielectric Surface Flashover at Atmospheric Conditions under High Power Microwave Excitation
  A. Neuber, J. T. Krile, G. F. Edmiston, H. G. Krompholz, "Dielectric Surface Flashover at Atmospheric Conditions under High Power Microwave Excitation", Phys. Plasmas 14, 057102 (2007) (invited).
Abstract:  Not Available
+ Dielectric Surface Flashover under Pulsed Unipolar and RF Excitation
  A. Neuber, “Dielectric Surface Flashover under Pulsed Unipolar and RF Excitation,” presented at the DPG Frühjahrstagung des AMOP, Düsseldorf, March 19-23, 2007, Germany (invited plenary presentation)
Abstract:  Not Available
+ Effects of UV Illumination on Surface Flashover under Pulsed Unipolar Excitation
  J. T. Krile, A. A. Neuber, H. G. Krompholz, "Effects of UV Illumination on Surface Flashover under Pulsed Unipolar Excitation," presented at the 2007 IEEE Pulsed Power and Plasma Science Conference, Albuquerque, NM June 17-22, 2007 (invited).
Abstract:  Not Available
+ Electro-Explosive Fuse Optimization for Helical Flux Compression Generator Using a Non-Explosive Test Bed
  D. McCauley, D. Belt, J. Mankowski, J. Dickens, A. Neuber, M. Kristiansen, "Electro-Explosive Fuse Optimization for Helical Flux Compression Generator Using a Non-Explosive Test Bed," presented at the 2007 IEEE Pulsed Power and Plasma Science Conference, Albuquerque, NM June 17-22, 2007.
Abstract:  Helical Flux Compression Generators (HFCG) of 50 mm form factor have been shown to produce a maximum energy deposit of 3 kJ into a 3 muH inductor from a seed current. A large dl/dt into a coupled load is possible when an electro-explosive fuse is used. Previous work with a non-optimized fuse has produced ~100 kV into a 15Omega load which leads into a regime relevant for High Power Microwave (HPM) systems. It is expected that ~3()0kV can be achieved with the present 2 stage HFCG driving an inductive storage system with an electro-exploding fuse. In order to optimize the electro-explosive fuse design, a non-explosive test bed, which closely simulates the 45 kA HFCG output, is used. To optimize the tiise, effects of fuse material, fuse length, and fuse shape will be examined as well as the effects of various quenching materials. Our previous work has characterized fuse material but we are also looking into the effects of the processes used to create the fuse wire, such as tempered wire versus fully annealed wire. Additionally, to maximize the output voltage and minimize the fuse recovery time, we are optimizing the length of the fuse wire. For shorter fuse lengths, we are optimizing fuse shape as well as fuse length to find the best fuse recovery time. By optimizing the individual parameters of an electro-explosive fuse, the fuse as a whole will be optimized to produce maximum output voltage when used with an HFCG.

[PDF]

+ Experimental investigation of subnanosecond gas breakdown in the E/p range 10^3 to 10^5 V/cm torr
  H. Krompholz, L. Hatfield, A. Neuber, P, J. Chaparro, and W. Justis, “Experimental investigation of subnanosecond gas breakdown in the E/p range 103 to 105 V/cm torr,” in Proceedings of the 28th ICPIG, July 15-20, 2007, Prague, Czech Republic, pp. 1014-1017.
Abstract:  Not Available
+ Fuse and Load Testing with Mid-Sized, High Energy Density Flux Compression Generators,
  A. J. Young, T. A. Holt, M. A. Elsayed, A. A. Neuber, M. Kristiansen, L. L. Altgilbers, A. H. Stults, "Fuse and Load Testing with Mid-Sized, High Energy Density Flux Compression Generators," presented at the 2007 IEEE Pulsed Power and Plasma Science Conference, Albuquerque, NM June 17-22, 2007.
Abstract:  Not Available
+ Initiation of HPM Surface Flashover
  G. F. Edmiston, A. A. Neuber, J. T. Krile, L. M. McQuage, H. Krompholz, "Initiation of HPM Surface Flashover," presented at the 2007 IEEE Pulsed Power and Plasma Science Conference, Albuquerque, NM June 17-22, 2007.
Abstract:  Not Available
+ Investigation of an FCG and Pulse Transformer Based Power Conditioning System
  T. A. Holt, A. J. Young, M. A. Elsayed, A. A. Neuber, M. Kristiansen, K. A. O'Connor, R. D. Curry, "Investigation of an FCG and Pulse Transformer Based Power Conditioning System," presented at the 2007 IEEE Pulsed Power and Plasma Science Conference, Albuquerque, NM June 17-22, 2007.
Abstract:  Not Available
+ Microprocessor based, Global Positioning System Guided Robot in a Project Laboratory
  Micheal Parten, Michael Giesselmann, Microprocessor based, Global Positioning System Guided Robot in a Project Laboratory, Paper: AC 2007-2528, American Society for Engineering Education, 2007 ASEE Annual Conference & Exposition, Honolulu, Hawaii, June 24-27, 2007.
Abstract:  Not Available
+ Modeling of a Single Element Pulsed Ring-Down Antenna for Implementation in a Phased Array System
  Belt, D.; Walter, J.; Mankowski, J.; Dickens, J.; Modeling of a Single Element Pulsed Ring-Down Antenna for Implementation in a Phased Array System; Pulsed Power Plasma Science, 2007. PPPS 2007. Conference Record - Abstracts. IEEE 17-22 June 2007 Page(s):816 - 816
Abstract:  Summary form only given. A pulsed ring-down phased array antenna provides substantial energy deposition in the far field region in addition to a broad range main beam with scanning capabilities. This allows remote neutralization of Improvised explosive devices (IEDs) at far field distances and in virtually any direction. The pulsed ring-down antenna operates by charging the single element antenna with a high potential source and closing a switch to develop transient wave reflections on the antenna which then propagate in air. The performance of a pulsed ring-down phased arrav is highly contingent upon the design and performance of the individual antenna elements within the array. Such factors as operating voltage, antenna capacitance, material losses, antenna geometry and closing switch conductance characteristics must be examined for optimal performance to be achieved. By utilizing the Comsol RF module transient analysis functions, we are able to characterize the various parameters beginning with a monopole and a dipole pulsed ring-down antenna operating in the hundreds of MHz range. We have examined and compared the results achieved from the experimental setup to the simulation model in order to better characterize the individual components of the antenna. We have also examined the discrepancies between an ideal closing switch and the experimental setup closing switch, which dramatically affects the far field range of the antenna. We have examined the material properties of the antenna to improve losses and increase system capacitance allowing an increase in the number of RF cycles per antenna discharge. With the results presented, an accurate model of pulsed ring-down antennas is available and will allow future development of more complex geometries that will improve the operation of pulsed ring- down phased array.

[PDF]

+ Opening Switch Utilizing Shock Wave Induced Conduction in PMMA and PVC
  C. Lynn, A. Neuber, J. Dickens, "Opening Switch Utilizing Shock Wave Induced Conduction in PMMA and PVC," presented at the 2007 IEEE Pulsed Power and Plasma Science Conference, Albuquerque, NM June 17-22, 2007
Abstract:  Not Available
+ Pulsed Volume and Surface Discharges in an SF6 Environment
  R. Vela, J. T. Krile, A. A. Neuber, H. G. Krompholz, "Pulsed Volume and Surface Discharges in an SF6 Environment," presented at the 2007 IEEE Pulsed Power and Plasma Science Conference, Albuquerque, NM June 17-22, 2007.
Abstract:  Not Available
+ Scaling Laws for Sub-Nanosecond Breakdown in Gases with Pressures below One Atmosphere
  W. H. Justis, J. E. Chaparro, H. G. Krompholz, L. L. Hatfield, A. A. Neuber, "Scaling Laws for Sub-Nanosecond Breakdown in Gases with Pressures below One Atmosphere," presented at the 2007 IEEE Pulsed Power and Plasma Science Conference, Albuquerque, NM June 17-22, 2007.
Abstract:  Not Available
+ Seed Electron Model for Monte Carlo HPM Breakdown Model
  A. Neuber, G. Edmiston1, H. Krompholz, “Seed Electron Model for Monte Carlo HPM Breakdown Model,” in Proceedings of the 28th ICPIG, July 15-20, 2007, Prague, Czech Republic, pp. 1042-1045.
Abstract:  Not Available
+ Short Pulse High Power Microwave Surface Flashover
  L. M. McQuage, G. F. Edmiston, J. P. Mankowski, A. A. Neuber, "Short Pulse High Power Microwave Surface Flashover," presented at the 2007 IEEE Pulsed Power and Plasma Science Conference, Albuquerque, NM June 17-22, 2007.
Abstract:  Not Available
+ Theoretical Pulsed Ring Down Antenna Array Performance
  Walter, J.; Dickens, J.; Mankowski, J.; Kristiansen, M.; Theoretical Pulsed Ring Down Antenna Array Performance Pulsed Power Plasma Science, 2007. PPPS 2007. Conference Record - Abstracts. IEEE 17-22 June 2007 Page(s):482 - 482
Abstract:  Summary form only given. High-power transient RF transmitters are currently being developed for multiple applications. One potential high- power pulsed source being considered is the pulsed ring- down source (PRDS). In a typical PRDS, electrical energy that is stored in the device structure is discharged through a switch, generating a damped ringing radiated waveform. The magnitude of the transmitted field is limited by parameters such as the overall device geometry and switch characteristics. The potential exists to increase the radiated far field power density by utilizing an array of PRDS transmitters. The performance of such an array depends on the triggering jitter of the device switches and the design of the individual radiating elements. The application of the array concept to pulsed ring-down sources using gas spark gap switches is examined. Theoretical array performance is discussed, taking into account practical switch jitter distributions, practical switch triggering schemes, and individual element characteristics.

[PDF]

+ X-Ray Emission from Sub-Nanosecond Gas Breakdown
  J. E. Chaparro, W. H. Justis, H. G. Krompholz, L. L. Hatfield, A. A. Neuber, "X-Ray Emission from Sub-Nanosecond Gas Breakdown," Proceedings of the 2007 IEEE Pulsed Power and Plasma Science Conference, pp. 1652-1655, Albuquerque, NM June 17-22, 2007.
Abstract:  Not Available
Publication Year:  2006
+ A Fabrication Method for a Mid-Sized, High Energy-Density, Flux Compression Generator
  T.A. Holt, A.J. Young, A.A. Neuber, M. Kristiansen, “A Fabrication Method for a Mid-Sized, High Energy-Density, Flux Compression Generator” presented at the 2006 International Conference on Megagauss Magnetic Field Generation and Related Topics, November 5-10, 2006 Santa Fe, New Mexico, USA
Abstract:  Not Available
+ A Fabrication Method for Helical Flux Compression Generators
  T.A. Holt, A.J. Young, A.A. Neuber, M. Kristiansen, “A Fabrication Method for Helical Flux Compression Generators,” presented at the 2006 Megagauss XI Conference, Sept. 10-14, 2006, Imperial College, London, UK
Abstract:  Not Available
+ A Flux Compression Generator Non-Explosive Test Bed for Explosive Opening Switches
  Belt, D.; Mankowski, J.; Neuber, A.; Dickens, J.; Kristiansen, M.; Conference Record of the 2006 Twenty-Seventh International Power Modulator Symposium, 2006. 14-18 May 2006 Page(s):456 - 459
Abstract:  Helical flux compression generators (HFCG) of a 50 mm form factor have been shown to produce output energies on the order of ten times the seeded value and a typical deposited energy of 3 kJ into a 3 muH inductor. Our previous work with a non-optimized fuse has produced-100 kV into a 15 load, which leads into a regime relevant for high power microwave (HPM) systems. It is expected that-300 kV can be achieved with the present 2-stage HFCG driving an inductive storage system with electro-exploding fuse. In order to optimize the electro-explosive wire fuse, we have constructed a non-explosive test bed which simulates the HFCG output with high accuracy. We have designed and implemented a capacitor based, magnetic switching scheme to generate the near exponential rise of the HFCG. The varying inductance approach utilizes 4 stages of inductance change and is based upon a piecewise linear regression model of the HFCG waveform. The non-explosive test bed will provide a more efficient method of component testing and has demonstrated positive initial fuse results

[PDF]

+ A Modular Approach to High Voltage, High Frequency Power Conversion at MW Power Levels
  Thomas Roettger, Michael Giesselmann, Brent McHale, Ryan Edwards, Wally Walavalkar, “A Modular Approach to High Voltage, High Frequency Power Conversion at MW Power Levels”, 2006 Advanced Naval Propulsion Symposium, Westin Arlington Gateway Hotel, Arlington, Virginia, Oct 30-31, 2006.
Abstract:  Not Available
+ Advanced Compact Pulsed Power for Directed Energy Weapons
  A. Neuber, “Advanced Compact Pulsed Power for Directed Energy Weapons,” Directed Energy Weapons and Laser Development Conference, January 18-19, Arlington, VA, 2006
Abstract:  Not Available
+ Contributing Factors to Window Flashover Under Pulsed High Power Microwave Excitation at High Altitude
  Edmiston, G.; Neuber, A.; Krile, J.; McQuage, L.; Krompholz, H.; Dickens, J.; 2006 Power Modulator Symposium, Conference Record of the 2006 Twenty-Seventh International May 2006 Page(s):389 - 392
Abstract:  One of the major limiting factors for the transmission of high power microwave (HPM) radiation is the interface between dielectric-vacuum, or even more severely, between dielectric-air if HPM is to be radiated into the atmosphere. Surface flashover phenomena which occur at these transitions severely limit the power levels which can be transmitted. It is of major technical importance to predict surface flashover events for a given window geometry, material and power level. When considering an aircraft based high power microwave platform, the effects on flashover formation due to variances in the operational environment corresponding to altitudes from sea level to 50,000 feet (760 Torr to 90 Torr) are of primary interest. The test setup is carefully designed to study the influence of each atmospheric variable without the influence of high field enhancement or electron injecting metallic electrodes.

[PDF]

+ Dielectric Surface Flashover at Atmospheric Conditions under High Power Microwave Excitation
  A. Neuber, “Dielectric Surface Flashover at Atmospheric Conditions under High Power Microwave Excitation,” APS conference, 2006 48th Annual Meeting of the Division of Plasma Physics, October 30-November 3, 2006, Meeting Id: DPP06, Philadelphia, PA. (invited)
Abstract:  Not Available
+ Dielectric Surface Flashover Research at Texas Tech University
  A. Neuber, H. Krompholz, J. Dickens, M. Kristiansen, “Dielectric Surface Flashover Research at Texas Tech University,” presented at the 1st Euro-Asian Pulsed Power Conference, Sept. 18 -22, 2006, Chengdu, China.
Abstract:  Not Available
+ Electro-explosive fuse development for helical flux compression generators
  D. Belt, J. Dickens, J. Mankowski, A. Neuber, and M. Kristiansen, “Electro-explosive fuse development for helical flux compression generators,” presented at the 2006 International Conference on Megagauss Magnetic Field Generation and Related Topics, November 5-10, 2006 Santa Fe, New Mexico, USA
Abstract:  Not Available
+ Helical Flux Compression Generator Non- Explosive Test Bed for Electro-Explosive Fuses
  D. Belt, J. Dickens, J. Mankowski, A. Neuber, M. Kristiansen, “Helical Flux Compression Generator Non- Explosive Test Bed for Electro-Explosive Fuses”, presented at the 27th Power Modulator Symposium and 2006 High Voltage Workshop May 14-18, 2006, Washington, DC.
Abstract:  Not Available
+ Interface Breakdown During High Power Microwave Transmission
  A. Neuber, J. Krile, G. Edmiston, H. Krompholz, J. Dickens, M. Kristiansen ,“Interface Breakdown During High Power Microwave Transmission,” presented at the 13th EML Symposium, May 22-25, 2006, Berlin, Germany.
Abstract:  Not Available
+ Pressure Induced Conductivity for High Power Switching
  Veselka, H.; Neuber, A.; Dickens, J.; Power Modulator Symposium, 2006. Conference Record of the 2006 Twenty-Seventh International 14-18 May 2006 Page(s):219 - 219
Abstract:  Summary form only given. Investigations of shock induced conductivity of non-crystalline insulators and crystalline semiconductors were performed. Although we measured the insulator-to-metallic state transition time and conductivity, the focus of this investigation was on the recovery phase of the induced conductivity (i.e. metallic-to-insulator state transition). The recovery time and shock conditions were measured with high speed electrical diagnostics. The goal of this research is to determine the feasibility of using shock induced conductivity as a means of producing a high power opening switch. To minimize switch losses, the insulator-to-metallic transition time and conductance is also important, but has been more widely studied. Initial impact studies have shown that certain insulator can be conductive for 100 microseconds and recover under modest voltage less than one microsecond using a ten gram explosive charge. Various shock intensities are used in the study. The shock is produced primarily with conventional commercial explosives. In addition, the impact of sample thickness and compression duration on the induced the conductivity were also studied. The correlation between modest voltage and high voltage recovery time and shut-off current were studied

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+ Pulsed Unipolar Surface Flashover at Atmospheric Conditions
  Morales, K.; Krile, J.; Neuber, A.; Krompholz, H.; Dickens, J.; Power Modulator Symposium, 2006. Conference Record of the 2006 Twenty-Seventh International 14-18 May 2006 Page(s):174 - 180
Abstract:  Dielectric surface flashover along insulators in vacuum has been comprehensively researched over the years. However, the primary mechanisms involved in dielectric flashover at atmospheric pressures have yet to be as extensively analyzed with variable parameters such as electrode geometry, background gas, humidity, and temporal characteristics of the applied voltage. Understanding the fundamental physical mechanisms involved in surface flashover at atmospheric pressures is vital to characterizing and modeling the arc behavior. Previous DC and unipolar excitation experiments have shown distinct arc behavior in air and nitrogen environments for an electrode geometry that produces electric field lines that curve above the dielectric surface. Specifically, flashover arcs in an air environment were observed to develop along the dielectric surface. Experiments conducted in nitrogen revealed that the arc developed along the electric field lines, above the surface of the dielectric. It was also of importance to alter the temporal characteristics of the applied voltage to simulate lightning situations and investigate the impact on the arc behavior and voltage delay times. A solid state high voltage pulser with an adjustable pulse width of ~500 ns at FWHM and amplitudes in excess of 30 kV was specifically developed to replicate the temporal characteristics of a voltage pulse observed when a building structure is hit by a lightning strike. Based on these results, the physical mechanisms primarily involved in pulsed unipolar surface flashover will be discussed. Additional studies regarding the effects of humidity and surface roughness on the flashover arc behavior will also be presented

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+ Rapid Capacitor Chargers for Rep-Rated Operation of Low-Inductance Compact Marx Generators
  Giesselmann, M.; McHale, B.; Neuber, A.; Conference Record of the 2006 Twenty-Seventh International Power Modulator Symposium, 2006. 14-18 May 2006 Page(s):588 - 591
Abstract:  We designed and tested several rapid capacitor chargers for rep-rated operation of low-inductance, compact Marx generators with rep-rates ranging from 10 Hz to 100 Hz. All chargers are designed to be packaged in cylindrical volumes with inside diameters in the range of 5 in-12 in. Our capacitor chargers are based on H-Bridge inverters using ultra fast 600 V class IGBTs. The high voltage is obtained by driving step-up transformers with nano-crystalline cores at 30 kHz. These chargers are capable of average DC output power levels of more than 5 kW for short time operation, during which the thermal inertia of the IGBT assembly provides effective cooling (up to seconds). To achieve reliable rep-rated operation of the chargers, we developed HV feedback sensors to monitor the charging process and solid state Marx-style trigger generators to command trigger the discharge of the main Marx

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+ Surface Flashover under RF and Unipolar Excitation at Atmospheric Conditions
  Krile, J.T.; Neuber, A.A.; Edmiston, G.F.; Krompholz, H.G.; Conference Record of the 2006 Twenty-Seventh International Power Modulator Symposium, 2006. 14-18 May 2006 Page(s):7 - 12
Abstract:  Flashover along insulators or insulating support structures has to be carefully addressed in the design of any DC, AC, or pulsed high voltage device. Although there is a large body of data on unipolar surface flashover in the atmosphere, which has led to empirical design rules primarily for the power distribution industry, the physics of the involved processes is widely unknown. The major limiting factor in the transmission of high power microwaves (HPM) into the atmosphere has been the vacuum-air interface. Both the unipolar and HPM surface flashover cases have been studied under vacuum conditions and have been found to have the same dominant mechanisms. Similarities between HPM window flashover on the air side and unipolar flashover are observed in an atmospheric environment as well

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+ The Impact of Water Conductivity, Electrode Material, and Electrode Surface Roughness on the Pulsed Breakdown Strength of Water
  Wetz, D.; Mankowski, J.; McCauley, D.; Dickens, J.; Kristiansen, M.; Conference Record of the 2006 Twenty-Seventh International Power Modulator Symposium, 2006. 14-18 May 2006 Page(s):104 - 107
Abstract:  Experimental results are presented on the impact water conductivity, electrode material, and electrode surface roughness have on the dielectric strength of water. A 2 mm water gap was tested under pulsed conditions with maximum electric fields in excess of 1.5 MV/cm. Bruce profiled electrodes manufactured from various materials including molybdenum, aluminum, copper, tungsten, nickel, stainless steel, and zinc oxide, which have work functions ranging from 4.2 eV to 5.3 eV, have been tested. The roughness average of the various surfaces was varied from 0.1 mum to 1.96 mum and the conductivity of the water within the gap was varied from 1muS/cm to 39 muS/cm to determine the impact each has when tested in combination with the various electrode materials and surface roughnesses. Conclusions are made as to the effect each of these factors has on the holdoff strength of a water dielectric system

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+ Transition of Window Breakdown from the Vacuum Multipactor Discharge to the Collisional RF Plasm
  Kim, H.C.; Verboncoeur, J.P.; Edmiston, G.F.; Neuber, A.A.; Lau, Y.Y.; Gilgenbach, R.M.; IEEE International Vacuum Electronics Conference, 2006 held Jointly with 2006 IEEE International Vacuum Electron Sources, 25-27 April 2006 Page(s):31 - 32
Abstract:  In high-power microwave systems, we investigate the transition of breakdown from single surface vacuum multipactor discharge to collisional rf plasma in argon. As the gas pressure increases, electron-neutral collisions prevail against secondary electron emissions. In addition, the discharge formation time is obtained as a function of the gas pressure.

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+ Ultrafast gas breakdown at pressures below one atmosphere
  Krompholz, H.; Hatfield, L.; Neuber, A.; Chaparro, J.; Ryu, H.-Y.; Justis, W.; 2006 IEEE Conference on Electrical Insulation and Dielectric Phenomena, 15-18 Oct. 2006 Page(s):569 - 572
Abstract:  Gas breakdown in quasi homogeneous electric fields with amplitudes of up to 3 MV/cm is investigated. The setup consists of a RADAN 303 A pulser and pulse sheer SN 4, an impedance-matched oil-filled coaxial line with a lens-transition to a biconical line in vacuum or gas, and an axial or radial gap with a width on the order of mm, with a symmetrical arrangement on the other side of the gap. Capacitive voltage dividers allow to determine voltage across as well as conduction current through the gap, with a temporal resolution determined by the oscilloscope sampling rate of 20 GS/s and an analog bandwidth of 6 GHz. The gap capacitance charging time and voltage risetime across the gap is less than 250 ps. Previous experiments at TTU with a slightly larger risetime have shown that breakdown is governed by runaway electrons, with multi-channel formation and high ionization and light emission in a thin cathode layer only. In argon and air, time constants for the discharge development have been observed to have a minimum of around 100 ps at several 10 torr. A qualitative understanding of the observed phenomena and their dependence on gas pressure is based on explosive field emission and gaseous ionization for electron runaway conditions.

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+ Virtual Cathode Oscillator Component Optimization
  Chen, Y.-J.; Mankowski, J.; Walter, J.; Kristiansen, M.; Conference Record of the 2006 Twenty-Seventh International Power Modulator Symposium, 2006. 14-18 May 2006 Page(s):157 - 160
Abstract:  Recent research efforts at TTU include a simple aluminum cathode for E-beam generation in a virtual cathode oscillator (vircator). As a continuation of these results, we are fabricating and testing several different types of cathodes for the vircator driven by a Marx generator and a pulse forming line (400 kV, 60 ns, 30 Omega). The cathodes, each with an emitting area of ~32 cm2, are made from aluminum and oxygen free copper fashioned to similar geometries with either a chemical etch or a CNC machine process. The vircator is tested with all of these cathodes and evaluated for beam voltage, current, and HPM generation. In addition to the cathode testing, several stainless steel and tungsten anode meshes with varying transparencies (50%-80%) are evaluated

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Publication Year:  2005
+ A Compact, Repetitive, 500kV, 500 J, Marx Generator
  Neuber, A.A.; Chen, Y.J.; Dickens, J.C.; Kristiansen, M.; 2005 IEEE Pulsed Power Conference; June 2005 Page(s):1203 - 1206
Abstract:  The electrical characteristics and design features of a low inductance, compact, 500 kV, 500 J, 10 Hz repetition rate, Marx generator are discussed. While benefiting from the large energy density of mica capacitors, 4 mica capacitors were utilized in parallel per stage, keeping the parasitic inductance per stage low. Including the spark-gap switches, a stage inductance of 55 nH was measured, which translates with 100 nF capacitance per stage to ~ 18.5 ¿ characteristic Marx impedance. Using solely inductors, ~ 1 mH each, as charging elements instead of resistors enabled charging the Marx within less than 100 ms with little charging losses. The pulse width of the Marx into a matched resistive load is about 200 ns with 50 ns rise-time. Repetitive HPM generation with the Marx directly driving a small Vircator has been verified. The Marx is fitted into a tube with 30 cm diameter and a total length of 0.7 m. We discuss the Marx operation at up to 21 kV charging voltage per stage, with repetition rates of up to 10 Hz in burst mode primarily into resistive loads. A lumped circuit description of the Marx is also given, closely matching the experimental results.

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+ A Low-Cost Metallic Cathode for a Vircator HPM Source
  Y.J. Chen, J.J. Mankowski, A. Neuber, J.C. Dickens, “A Low-Cost Metallic Cathode for a Vircator HPM Source,” Proceedings of the 15th Int. IEEE Pulsed Power Conference, pp. 66-69, Monterey, CA, June 13-17, 2005
Abstract:  Not Available
+ A Low-Cost Metallic Cathode for a Vircator HPM Source
  Mankowski, J.; Chen, Y.; Dickens, J.; Neuber, A.; Gale, R.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):66 - 69
Abstract:  Recent research efforts at TTU include the testing of a rapidly charged, rep-rated Marx generator driving a reflex triode vircator [1]. As expected, the burning of the cathode material (ordinary cloth velvet), was the primary failure mechanism during repetitive operation. In an effort to achieve a repetitive vircator (>10 Hz), we are exploring a low-cost, all-metal cathode. The cathode is made from aluminum with a patterned surface. A typical pattern is composed of peaks and troughs with dimensions on the order of tens of microns. The pattern is achieved with a simple, low-cost chemical etching process. Results include current, voltage, and microwave waveforms from two solid metal cathodes and a cloth velvet cathode.

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+ An Ion Beam Sputtering System for Electrode Surface Conditioning
  Wetz, D.; Mankowski, J.; Kristiansen, M.; IEEE Conference Record - Abstracts. IEEE International Conference on Plasma Science, 2005. ICOPS '05. 20-23 June 2005 Page(s):123 - 123
Abstract:  Summary form only given. In the past there has been considerable research performed using electromagnetic plasma thrusters as the primary ion source in sputtering applications. In the experiments conducted here, thin film coatings of various hard metallic alloys and oxides were applied to stainless steel electrodes using ion beam deposition. An SPT type Hall effect thruster capable of producing an ion beam with energies between 150 eV and 350 eV was used as the deposition ion source. The surface coatings were applied to Bruce profiled stainless steel electrodes which have an effective surface area of 5 cm2 and a roughness average of roughly 70 nm. The electrodes were then examined using an optical profiler to accurately measure the roughness average of the thin film coating as well as the effective layer thickness. A comparison of the results obtained from each surface material is performed

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+ Autonomous RF Radiation Package for EW Applications
  W.J. Carey, A.J. Wiebe, D.D. Schwindt, ARC Technology, Whitewater, KS, L.L Altgilbers, US Army Space and Missile Defense Command, Huntsville, AL, M. Giesselmann, B. McHale, K. Heinemann, TTU, Lubbock, TX, “Autonomous RF Radiation Package for EW Applications”, Proceedings of the 15th IEEE Pulsed Power Conference, June 13-17, 2005, Monterey, California.
Abstract:  Not Available
+ Bubble Dynamics and Channel Formation for Cathode Initiated Discharges in Transformer Oil
  Cevallos, M.; Butcher, M.; Dickens, J.; Neuber, A.; Krompholz, H.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):1235 - 1238
Abstract:  The development of cathode initiated low density channel formation and propagation leading to self breakdown in transformer oil is investigated using high speed electrical and optical diagnostics in a coaxial system with a point/plane axial discharge at various hydrostatic pressures. A cathode initiated channel formation and propagation model based upon single bubble dynamics has been presented by Kattan [1]. Experiments based on high-speed shadowgraphy were conducted to decide if the principles that govern single bubble dynamics could be applied to cathode initiated channel formation. These experiments show bubble motion away from the cathode, with separation velocities on the order of 10's m/s. This separation is similar for single bubbles generated at the cathode and for bubble chains developing into low-density channels. Lifetimes of these channels are recorded and show good correlation with the Rayleigh model [2] used to predict lifetimes of single bubbles. Experiments at reduced hydrostatic pressure reveal a critical pressure below which low density channel expansion occurs, further corroborating the presence of a gas phase. Finally, the pressure dependence of the breakdown voltage due to the expansion of the low density channels is examined and a model for this dependence is presented. The experiments conducted confirm the presence of a gas phase channel, its correlation with single bubble dynamics, and its importance to final breakdown.

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+ Characaterization of Transient Antennas
  "Characaterization of Transient Antennas", proceeding of the 15th Int’l. Pulsed Power Conference, Monterey, CA, June 13-17, 2005 (with J. Walter and J. Dickens).
Abstract:  Not Available
+ Compact Pulsed Power at TTU
  A. Neuber, M. Kristiansen, J. Dickens, M. Giesselmann, “Compact Pulsed Power at TTU,” 3rd Annual Multi-Functional Warhead Workshop, 30 November – 1 December 2005, Redstone Arsenal, Huntsville, AL.
Abstract:  Not Available
+ Composite Shadowgraphy and Luminosity Images of Self Breakdown Discharge Channels in Transformer Oil
  Cevallos, M.; Butcher, M.; Dickens, J.; Neuber, A.; Krompholz, H.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):982 - 985
Abstract:  The physics of cathode initiated discharge formation leading to self breakdown in transformer oil is investigated using high speed electrical and optical diagnostics in a coaxial system with a point/plane axial discharge. Previous research conducted on self breakdown channel formation using high speed shadowgraphy and photography of the emitted light has shown tree-like structures for both cathode and anode initiated discharges, with characteristic differences. Cathode initiated discharges expand faster to a more "bushy" appearance, whereas anode initiated discharges show branching localized channels. So far, the spatial resolution to detect small luminous areas in pre-breakdown discharges and to determine their correlation to low density regions visible in the shadowgraphs was not sufficient in the experiments described in this paper, thus a systematic variation of exposure times, and time delays between luminosity pictures and shadowgraphy pictures has been performed. These experiments confirm that the luminosity emitted during prebreakdown events is generated from the low density regions seen in the shadowgraphy images, indicating charge amplification mechanisms in the gas phase for cathode initiated events. This statement is further supported by the dependence of both the channel dynamics and the light emission at lowered hydrostatic pressure.

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+ High Power Microwave Breakdown Limits of Dielectric/Gas Interfaces
  A. Neuber, G. Edmiston, J. Krile, K. Morales, J. Dickens, H. Krompholz, "High Power Microwave Breakdown Limits of Dielectric/Gas Interfaces,” presented at the 2005 International COE Forum on Pulsed Power Science held on November 13 – 14 at Kumamoto, Japan. (invited)
Abstract:  Not Available
+ High Power Microwave Surface Flashover of a Gas-Dielectric Interface at 90 to 760 Tor
  Edmiston, G.; Krile, J.; Neuber, A.; Dickens, J.; Krompholz, H.; 2005 IEEEPulsed Power Conference, June 2005 Page(s):350 - 353
Abstract:  The major limiting factor in the transmission of HPM has been the interface between dielectric-vacuum or even more severely between dielectric-air if HPM is to be radiated into the atmosphere. Extensive studies have identified the physical mechanisms associated with vacuum-dielectric flashover, as opposed to the mechanisms associated with air-dielectric flashover, which are not as well known. Surface flashover tests involving high field enhancement due to the presence of a triple point have shown that volume breakdown threshold (dielectric removed) is approximately 50% higher than the flashover threshold with a dielectric interface over the 90-760 torr range [1]. In order to quantify the role of field enhancement in the flashover process independent of electron injection from metallic surfaces, the effects of the triple point are minimized by carefully choosing the geometry and in some cases the triple point is "removed" from the flashover location. We will present experimental results, including the impact of gas pressure, and discuss possible causes for the difference in the rf-breakdown field with and without the interface/metallic triple point portion.

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+ High Voltage Impulse Generator Using HV-IGBTs
  Giesselmann, M.; Palmer, B.; Neuber, A.; Donlon, J.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):763 - 766, Monterey, California.
Abstract:  We are reporting on a High-Voltage Impulse Generator, which consists of a step-up transformer, which is driven by new HV-IGBTs (High-Voltage Isolated Gate Bipolar Transistors). The new HV-IGBTs are individually packaged silicon-dies intended for Pulsed-Power Applications. The silicon dies are normally packaged in large modules for locomotive motor drives and similar traction applications. In our work we used the Powerex QIS4506001 discrete IGBT and the QRS4506001 discrete diode, both with a nominal rating of 4500V/60A, derived from continuous-duty applications. Our experiments have shown that the devices are capable of handling currents in excess of 1 kA during pulsed operation.

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+ Investigation of Charge Conduction and Self-Breakdown in Transformer Oil
  Butcher, M.; Cevallos, M.; Neuber, A.; Krompholz, H.; Dickens, J.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):1143 - 1146
Abstract:  With a fast coaxial setup using a needle/plane geometry and a high sensitivity electrometer, conduction mechanisms in transformer oil at varying temperature and hydrostatic pressure are quantified. There are 3 stages in the conduction process prior to breakdown for highly nonuniform field geometries. Stage I is characterized by a resistive current at low fields. Stage II consists of a rapid rise in the injection current associated with increasing field due to a "tunneling" mechanism through the metal/dielectric interface. The transition from the resistive to tunneling stage occurs when the applied field reduces the barrier at the metal/insulator interface to a point where tunneling of charge carriers through the barrier begins. This transition point is polarity dependent. In stage III, at high fields the current reaches space charge saturation at electron mobilities >100 cm2/V*s prior to breakdown. The processes of final breakdown show distinct polarity dependence. Data for the negative needle exhibits strong pressure dependence of the breakdown voltage, which is reduced by 50% if the hydrostatic pressure is lowered from atmospheric pressure to hundreds of mtorr. Such a strong pressure dependence, at reduced hydrostatic pressure, indicates breakdown is gaseous in nature. This is supported by images of bubble/low density regions forming at the current injection point. Positive needle discharges show a reduction of only about 10% in breakdown voltage for the reduced pressure case. A weak pressure dependence indicates the breakdown mechanism does not have a strong gaseous component. We will discuss possible links between conduction current and DC breakdown.

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+ Limits of High Power Microwave Transmission due to Interface Breakdown
  A. Neuber, J. Krile, G. Edmiston, H. Krompholz, J. Dickens, "Limits of High Power Microwave Transmission due to Interface Breakdown," presented (oral) at 2005 Tri-Service VED Workshop, 12-16 September 2005
Abstract:  Not Available
+ Multi-Frequency and Multi-Mode Microwave Identification in a Vircator Research
  Xupeng Chen; Dickens, J.C.; Hatfield, L.L.; Mankowski, J.; Kristiansen, M.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):190 - 193
Abstract:  In virtual cathode oscillator (VIRCATOR) research, multi-frequency and multi-mode microwaves are coupled out and propagate along a waveguide. Identifying the microwave propagating modes has become a priority work for further research on microwave radiation physical mechanisms. Generally, an antenna matrix at the end of an open waveguide, which can shape the radiated microwave power distribution, is used to identify the microwave propagating modes [1-2]. Actual microwave radiation mechanisms in a VIRCATOR are complicated. Multi propagating modes and multifrequency microwaves coexist simultaneously, which challenges the antenna matrix method. In this paper, based on microwave propagating theory in a waveguide, a new method is proposed to identify multi-frequency and multi-mode microwaves, which is partially justified by the experimental data at Texas Tech University.

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+ Multistage Helical Flux Compression Generator Non-Explosive Test Bed
  Belt, D.; Dickens, J.; Mankowski, J.; Neuber, A.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):525 - 528
Abstract:  Helical Flux Compression Generators of small dimensions have been shown to produce energy output around 3 kJ into an inductive load. Adding a fuse opening switch has allowed us to produce 300kV into a 15 Ohm load. We are investigating inductive energy storage with emphasis on an electro-explosive fuse opening switch in order to improve upon previous results. We have designed and constructed a non-explosive test bed composed of two pulse forming networks (PFN). Each PFN provides a linear approximation during two different time ranges of the exponential rise response of a typical HFCG. This approach will be more cost and time effective than to drive the fuse with an explosive generator. Our initial goal will be to simulate a 15 kA HFCG unit followed by the simulation of a 50 kA HFCG.

[PDF]

+ Pulsed Dielectric Surface Flashover at Atmospheric Conditions
  Morales, K.P.; Krile, J.T.; Neuber, A.A.; Krompholz, H.G.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):1147 - 1150
Abstract:  Dielectric flashover along insulators in vacuum has been sufficiently researched in the past. Less studied, but of similar importance, is surface flashover at atmospheric pressures and the impact of various electrode geometries, humidity, and type of gas present. Previous research has shown distinct arc behavior in air and nitrogen for an electrode geometry in which the electric field lines curve above the dielectric surface. Specifically, flashover experiments in nitrogen have shown that the arc path will follow the electric field lines, not the dielectric surface. As a result, it was concluded that the arc development path, whether along the electric field line or the surface of the dielectric, is related to the oxygen content in the atmospheric background [1]. It is believed that this dependence is due to the arc's production of UV radiation in an oxygen rich environment. Further testing, in a pure nitrogen environment with UV illumination of the surface prior to the pulse application, has shown that UV plays a significant role in the arc development path. There is a near linear relationship between the percentage of liftoffs and the time delay between UV application and flashover. Additional studies have also shown a relationship between the UV intensity and the percentage of liftoffs. Based on these results we will discuss the physical mechanisms primarily involved in unipolar flashover at atmospheric pressure. Additional experimental results regarding the effects of humidity on the liftoff phenomenon will be presented as well.

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+ Rapid Capacitor Charger for 10 Hz Operation of a Low-Inductance Compact Marx Generator
  M. Giesselmann, B. McHale, “Rapid Capacitor Charger for 10 Hz Operation of a Low-Inductance Compact Marx Generator”, Proceedings of the 15th IEEE Pulsed Power Conference, June 13-17, 2005, Monterey, California.
Abstract:  Not Available
+ Shock Induced Conductivity for High Power Switching
  Veselka, H.; Neuber, A.; Dickens, J.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):734 - 737
Abstract:  Investigations of shock induced conductivity of insulators and semiconductors both crystalline and non-crystalline, were performed. Although the insulator-to-metallic state transition time was measured, the focus of this investigation was on the recovery phase of the induced conductivity (i.e. metallic-to-insulator state transition). The recovery time and shock conditions were measured with high speed electrical diagnostic equipment. The goal of this research is to determine the feasibility of using shock induced conductivity as a means of producing a high power opening switch. To minimize switch losses, the insulator-to-metallic transition time and conductance is also important, but has been more widely studied. Various shock profiles and intensities and used in the study. The shock is produced primarily with conventional commercial explosives. Shock reverberation is planed in some tests to minimize sample heating and to produce tailored shock time profiles. In addition, the impacts of sample thickness and compression duration on the induced conductivity were also studied.

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+ Similarities of Dielectric Surface Flashover at Atmospheric Conditions for Pulsed Unipolar and RF Excitation
  Krile, J.; Edmiston, G.; Neuber, A.; Dickens, J.; Krompholz, H.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):354 - 357
Abstract:  Mechanisms in vacuum flashover caused by rf (f<10 GHz) or unipolar voltages are virtually identical. Similarities between rf (representing high power microwave window breakdown on the high pressure side) and unipolar flashover are expected in an atmospheric environment as well. Our experimental setups enable studying both unipolar flashover and rf window flashover at atmospheric conditions while controlling excitation, temperature, pressure, humidity, and type of gas present. The local electric field at the flashover initiating points has been numerically calculated in detail for all test geometries. For both rf and unipolar pulsed excitation, the flashover dynamics are changed by the application of UV light to the dielectric surface. A UV pre-pulse has a distinct impact on the arc's path and a tendency to increase the hold-off electric field. The effect of humidity on the hold-off electric field for both pulsed unipolar and rf excitations, along with temporally resolved emission spectroscopy of the flashover event, will be discussed.

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+ Simulation Studies of Liquid Water Breakdown By a Sub-Microsecond Pulse
  Qian, J.; Joshi, R.P.; Kolb, J.; Schoenbach, K.H.; Dickens, J.; Neuber, A.; Cevallos, M.; Krompholz, H.; Schamiloglu, E.; Gaudet, J.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):738 - 741
Abstract:  An electrical breakdown model for liquids in response to a sub-microsecond (~ 100 ns) voltage pulse is presented, and quantitative evaluations carried out. It is proposed that breakdown is initiated by field emission at the interface of pre-existing micro-bubbles. Impact ionization within the micro-bubble gas then contributes to plasma development, with cathode injection having a delayed and secondary role. Continuous field emission at the streamer tip contributes to filament growth and propagation. This model can adequately explain almost all of the experimentally observed features, including dendritic structures and fluctuations in the pre-breakdown current. Two-dimensional, time-dependent simulations have been carried out based on a continuum model for water, though the results are quite general. Monte Carlo simulations provide the relevant transport parameters for our model. Our quantitative predictions match the available data quite well, including the breakdown delay times and observed optical emission. energy associated with a sub-microsecond pulse is too low to induce any significant heating [2]. Temperature increases of less than 6 K were predicted. Hence, bubble formation on the basis of localized liquid vaporization can effectively be ruled out. Here a general model of liquid breakdown is developed that incorporates two important features. First, the preexistence of spatially localized micro-bubbles, in equilibrium with the liquid phase, is implicitly assumed. As a result, no strong internal heating or vaporization is necessary for the creation of local low-density regions. Such bubbles are assumed to be filled with dissolved gas.

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+ Subnanosecond Breakdown in Argon at High Overvoltages
  Krompholz, H.; Hatfield, L.L.; Neuber, A.; Hemmert, D.; Kohl, K.; Chaparro, J.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):423 - 426
Abstract:  Volume breakdown and surface flashover in quasi homogeneous applied fields in 10-5 to 600 torr argon are investigated, using voltage pulses with 150 ps risetime, < 1 ns duration, and up to 150 kV amplitude into a matched load. The test system consists of a transmission line, a transition to a biconical section, and a test gap, with gap distances of one to several mm. The arrangement on the other side of the gap is symmetrical. An improved system, with oil-filled transmission lines and lens between coax and biconical section to minimize pulse distortion, is being constructed. Diagnostics include fast capacitive voltage dividers, which allow to determine voltage waveforms in the gap, and conduction current waveforms through the gap. X-ray diagnostics uses a scintillator-photomultiplier combination with different absorber foils yielding coarse spectral resolution. Optical diagnostics to obtain information about the discharge channel dynamics is in preparation. Breakdown delay times, and e-folding time constants for the conduction current during the initial breakdown phase, are on the order of 100-400 ps, with minima in the range of several 10 torr. X-ray emission extends to pressures > 100 torr, indicating the role of runaway electrons during breakdown. Maximum x-ray emission coincides with fastest current risetimes at several 10 torr, which is probably related to an efficient feedback mechanism from gaseous amplification to field enhanced electron emission from the cathode.

[PDF]

+ The Impact of Electrode Area and Surface Roughness on the Pulsed Breakdown Strength Water
  Wetz, D.; Mankowski, J.; Kristiansen, M.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):1163 - 1166
Abstract:  Experimental results are presented on the degree to which electrode surface area and surface roughness impacts the dielectric strength of water. A 2 mm water gap was tested under pulsed conditions with maximum electric fields in excess of 1 MV/cm and maximum currents of more than 5 kA. Six different pairs of stainless steel electrodes, each having a unique Bruce profile and thus a different effective surface area, were used to achieve a uniform electric field across the gap. The differing electrode pair profiles, with effective areas ranging from 0.5 cm2 to 76 cm2, were designed to minimize the change in gap capacitance. Prior to each test, a different roughness average, ranging from 0.26 ¿m to 1.96 ¿m, was applied to the electrodes. Conclusions are made as to the effect both electrode surface area and surface roughness has on the holdoff voltage of water dielectric systems. In addition, shadowgraph images of pre-breakdown events are presented.

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+ The Impact of Electrode Material on the Pulsed Breakdown Strength of Water
  Wetz, D.; Mankowski, J.; Dickens, J.; Kristiansen, M.; 2005 IEEE Pulsed Power Conference, June 2005 Page(s):935 - 938
Abstract:  In the experiments presented here, various electrode materials were tested in an effort to determine the impact each has on increasing the dielectric strength of water. Prior investigations have tested materials such as stainless steel, copper, nickel, gold, silver, and cuprous oxide [1-4]. In our experiments, thin film coatings of various metallic alloys and oxides were applied to Bruce profiled stainless steel electrodes with an effective area of 5 cm2. An ion beam sputtering process was used to apply the coatings with thicknesses of several hundred nm. The electrodes were then tested across a water gap, with pulse lengths in both the microsecond and nanosecond time regimes. Electric fields in excess of 8 MV/cm were applied. Conclusions are made as to the impact electrode material has on the pulsed breakdown strength of water.

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Publication Year:  2004
+ Compact FCG Driven Inductive Energy Storage System
  J.-C. Hernandez, A. A. Neuber, M. Giesselmann, J. C. Dickens, and Magne Kristiansen, ”Compact FCG Driven Inductive Energy Storage System,” in Proceedings of MegaGauss X, Berlin, Germany, July 18 -23, p. 144-147, 2004,.
Abstract:  Not Available
+ Compact Pulsed Power
  "Compact Pulsed Power", 5th International Sy mposium on Pulsed Power and Plasma Applications, Chang Won, Gyeong-Nam, Korea. October 18-21, 2004.
Abstract:  Not Available
+ Compact Pulsed Power
  M. Kristiansen, J. Dickens, H. Krompholz, M. Giesselmann, A. Neuber, J. Mankowski, L. Hatfield, “Compact Pulsed Power,“ Proceedings of the 5th International Symposium on Pulsed Power and Plasma Applications, Oct. 18-20, Chan-Won, Korea, p. 10-15, 2004. (Invited paper)
Abstract:  Not Available
+ Compact Pulsed Power
  M. Kristiansen, A. Neuber, J. Dickens, M. Giesselmann, and S. Shkuratov, “Compact Pulsed Power,“ MegaGauss X, Berlin, Germany, July 18 -23, p. 169-175, 2004. (Invited)
Abstract:  Not Available
+ DC and Pulsed Dielectric Surface Flashover at Atmsopheric Pressure
  J. T. Krile, A. Neuber, H. G. Krompholz, and J. C. Dickens, „DC and Pulsed Dielectric Surface Flashover at Atmsopheric Pressure,“ 2004 Power Modulator Conference, San Francisco, CA, 2004.
Abstract:  Not Available
+ Effect of temperature and pressure on DC pre-breakdown current in transformer oil
  Butcher, M.; Neuber, A.; Krompholz, H.; Dickens, J.; IEEE Conference Record - Abstracts. The 31st IEEE International Conference on Plasma Science, 2004. ICOPS 2004. 28 June-1 July 2004 Page(s):258
Abstract:  Summary form only given. Any attempt to model the complex interaction of hydrodynamic and electronic processes leading to breakdown in transformer oil suffers from the lack of microscopic transport data. Also, interface processes, such as electron emission from metal electrodes immersed in liquid, are poorly understood. As a first step toward the understanding of breakdown phenomenology, the voltage-current characteristics for pre-discharge conditions are measured. An experimental setup was constructed which allows temperature variations between 10/spl deg/C and 50/spl deg/C, at pressures between 0.5 and 3 bar. DC currents ranging from a few nA with a few kV of applied voltage, to a few /spl mu/A prior to full breakdown are measured using an electrometer. Preliminary results at NTP with a tip-plane geometry indicate Ohmic behavior at low voltages, Schottky emission at intermediate voltages, and saturation due to space charge at high voltages, and allow estimates on the physical parameters governing these effects. The indicated temperature range of the measurements is associated with a variation of the viscosity of a factor of 3, where we anticipate similar relative changes for the transport of electrons. The intermediate voltage range where a Schottky emission process is assumed will be emphasized. For instance, the electron mobility, derived from experimental data to about 0.06 cm/sup 2//Vs at NTP in the intermediate voltage range should distinctly vary with changing temperature and pressure.

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+ Electrical breakdown in transformer oil
  Cevallos, M.D.; Dickens, J.C.; Neuber, A.A.; Krompholz, H.G.; IEEE Conference Record - Abstracts. The 31st IEEE International Conference on Plasma Science, 2004. ICOPS 2004. 28 June-1 July 2004 Page(s):401
Abstract:  Summary form only given. The fundamental breakdown physics of transformer oils is investigated with high-speed electrical and optical diagnostics with temporal resolution down to 500 ps. Univolt 63 and Envirotemp FR3 (biodegradable) are used for this study. The system set up employs a cable discharge into a coaxial system with point/plane axial discharge and load line to providing a matched terminating impedance. Overall, the impedance of the system is matched at 50 ohms throughout with the exception of the very narrow gap region and includes a 50 ohm load resistor terminating the load line. Self breakdown is achieved by applying up to 50 kV to the charging line. Pulsed breakdown is achieved by charging a pulse forming line with a two way transient time of 300 ns, up to 100 kV. The pulse forming line is then fed into the discharge line via an oil spark gap. Transmission line type current sensors and a capacitive voltage divider with fast amplifiers/attenuators are used in order to attain a complete range of information from amplitudes of 0.1 mA to 1 kA with temporal resolutions of 300 ps. Optical measurements are performed on low level light emission using fast photo-multiplier tubes (risetime of 800 ps) spatially resolved, supplemented with high speed and spectroscopic investigations on a nanosecond timescale. Breakdown voltages at gap distances of 5 mm for pre, self, and pulsed breakdown voltages are given, where breakdown with negative needle tips show 20% higher breakdown voltages than the ones with positive needle. Velocities of propagating "tree"-structures for the pre and self-breakdown are a few km/s while pulsed breakdown velocities are several 10's of km/s, with higher velocities for a negative needle. The trees have to reach the opposite electrode before full breakdown occurs. Simultaneous optical measurements for a single breakdown event are presented, such as the luminosity in comparison to shadowgraphy images, which is necessary to describe the complex interaction of hydrodynamic phenomena (channel and tree formation and propagation) and charge carrier multiplication.

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+ Explosive Pulsed Power Sources for Directed Energy Weapons
  A. Neuber, M. Giesselmann, "Explosive Pulsed Power Sources for Directed Energy Weapons”, invited presentation at the 2004 Directed Energy Symposium, Rockville, Maryland
Abstract:  Not Available
+ Fast Volume Breakdown in Argon and Air at Low Pressures
  E. Crull, H. Krompholz, A. Neuber, and L. Hatfield, “Fast Volume Breakdown in Argon and Air at Low Pressures,” Euro Electromagnetics, Magdeburg, Germany, July 12-16, 2004.
Abstract:  Not Available
+ Fast, Transient Energy Extraction from high Frequency AC-Alternators for use in Electromagnetic Launch Applications
  M. Giesselmann, B. McHale, M. Crawford, “Fast, Transient Energy Extraction from high Frequency AC-Alternators for use in Electromagnetic Launch Applications”, 12th EML Symposium, May 25-28, 2004, Snowbird, Utah.
Abstract:  Not Available
+ Forward and Reverse Recovery SPICE Model of a JBS Silicon Carbide Diode
  R. Edwards, M. Giesselmann, S. Bayne, S. Kaplan, and E. Shaffer, “Forward and Reverse Recovery SPICE Model of a JBS Silicon Carbide Diode”, Proceedings of the 2004 Power Modulator Conference & High Voltage Workshop, San Francisco, California, May 23-26, 2004.
Abstract:  Not Available
+ High Power Microwave Breakdown of a Gas-Dielectric Interface at 90 to 760 Torr
  G. Edmiston, A. Neuber, H. Krompholz, J. Dickens, "High Power Microwave Breakdown of a Gas-Dielectric Interface at 90 to 760 Torr,” presented at the 46th Annual Meeting of the Division of Plasma Physics November 15-19, 2004, Savannah, GA, Meeting ID: DPP04APS
Abstract:  Not Available
+ Impact of surface conditioning of large area electrodes on the dielectric strength of water
  Wetz, D.; Mankowski, J.; Truman, K.; Kristiansen, M.; Conference Record of the Twenty-Sixth International Power Modulator Symposium, 2004 and 2004 High-Voltage Workshop. 23-26 May 2004 Page(s):512 - 515
Abstract:  Experimental results are presented on the impact electrode material and surface treatment has on the dielectric strength of water. A 4 mm water gap was tested under pulsed conditions with pulse widths greater than 1 /spl mu/s, peak electric fields over 2 MV/cm and peak currents over 15 kA. 304 stainless steel electrodes machined with a Bruce profile and an effective area of 5 cm/sup 2/ were tested with surface roughnesses ranging from .34 /spl mu/m to 1.41 /spl mu/m. Results comparing electrodes that have additionally been electropolished are compared to those without an additional treatment. These various surface treatments remove microprotrusions from the electrode's surface which reduce field enhancements across the electrode surface. It is believed that this technique will minimize the number of breakdown initiation points thereby increasing the dielectric strength. Results are given on the degree to which each finish improves the dielectric strength of water.

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+ Light-matter interaction in transformer oil
  Namihira, T.; Wang, D.; Neuber, A.; Butcher, M.; Dickens, J.; Krompholz, H.; IEEE Conference Record - Abstracts. The 31st IEEE International Conference on Plasma Science, 2004. ICOPS 2004. 28 June-1 July 2004 Page(s):448
Abstract:  Summary form only given. Considering highly stressed dielectric liquids, the role of mechanisms such as photoionization in the liquid volume or photoeffect at the cathode for the development of dielectric breakdown is investigated. We used a pulsed 300 W Xenon light source (25 mm output window, 5 degree divergence) with a broad spectral range of 200 to 1100 nm to study the impact of the light beam focused either solely on the high field region between the breakdown electrodes or including the electrodes. Typical field strengths in the electrode gap (/spl sim/4 mm gap, 3 mm tip radius,) were 15 to 25 kV/cm resulting in a DC current amplitude (without light) of up to 2 nA (apparatus resolution /spl sim/10 pA). Standard transformer oil, Univolt 61, and a biodegradable oil, Environtemp FR3 (natural ester fluid), were examined in the present work. Both oils exhibit strong optical absorption in the UV. However, Univolt 61 has its cut off wavelength at 450 nm, while bio oil easily transmits down to 350 nm. Below the cutoff wavelength, virtually all radiation is absorbed within a few mm. When pulsing the Xenon lamp at /spl sim/500 microsec no increase in DC current amplitude (increase <10 pA) could be detected for either oil. Increasing the pulse length to several seconds lead to a distinct increase in current amplitude (up to 300 pA), however, only for Univolt 61. Such an increase in current amplitude can also be achieved by raising the temperature of the dielectric liquid by external heating (/spl sim/100 pA/K). The temperature levels leading to similar current amplitudes due to heating by the Xenon lamp or external heating are comparable. Since bio oil absorbs only below 350 nm, the temperature rise due to the light irradiation was comparably smaller than in Univolt 61. Thus, any heating and increase in current were less pronounced in bio oil. For both oils, the observed behavior can be entirely explained by thermal effects. Both, photoionization and photoeffect have seemingly a minor impact on breakdown development. The detailed discussions are given in the present work.

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+ Modeling of Pulsed Radiating Structures
  "Modeling of Pulsed Radiating Structures", 2nd European Pulsed Power Symposium 2004, Hamburg, Germany, September 20-23, 2004 (with John Walter and J. Dickens).
Abstract:  Not Available
+ Nanosecond, optical diagnostics for liquid dielectric switches
  Kolb, J.F.; Xiao, S.; Goan, B.; Lu, X.P.; Schoenbach, K.H.; Laroussi, M.; Joshi, J.P.; Dickens, J.; Neuber, A.; Krompholz, H.; Cevallos, M.; Butcher, M.; IEEE Conference Record - Abstracts. The 31st IEEE International Conference on Plasma Science, 2004. ICOPS 2004. 28 June-1 July 2004 Page(s):402
Abstract:  Summary form only given. The high dielectric strength of liquid dielectrics allows for the design of small, low inductance and consequently fast high power switches. The investigation of the streamer formation which eventually leads to electrical breakdown requires diagnostic techniques with high temporal and spatial resolution. Optical methods, such as interferometry, Schlieren photography and shadowgraphy have been used to study the development of streamers and subsequent spark channel formation and decay in a pin-plane geometry. The temporal resolution is determined by the shutter speed of a high-speed camera, and was generally on the order of 1 ns. Interferometric measurements in water under high dielectric stress allowed for the characterization of the transient electric field distribution up to the imminent breakdown. Schlieren and shadow photographs allowed us to explore the development of the discharge and the switch recovery. With the pin electrode being the cathode tree-shaped inhomogeneities expand into the gap before breakdown is initiated by the formation of a single streamer that eventually bridges a gap of 400 /spl mu/m in about 7 ns. The recovery is determined by the formation of a vapor bubble that is cleared from the gap in about 1 ms. In oil, the processes involving the interaction of hydrodynamic and electronic processes are more complex. DC breakdown in a pin-plane geometry is strongly polarity dependent. Successively growing trees are observed, which bridge a 1-mm gap after as much as 1 /spl mu/s causing large breakdown delays. For fast pulse breakdown, the observed phenomena resemble more the ones observed in water. Gaining complete information on the breakdown phenomenology in oil requires the simultaneous use of all diagnostics methods including high resolution current measurements. Of special importance is information on the propagation of gaseous channels involved in the tree formation, and measurement of the correlated light emission indicating charge carrier amplification.

[PDF]

+ New Developments in High Power Capacitor Charging Technology
  M. Giesselmann, B. McHale, “New Developments in High Power Capacitor Charging Technology”, Proceedings of the 2004 Power Modulator Conference & High Voltage Workshop, San Francisco, California, May 23-26, 2004.
Abstract:  Not Available
+ Power Conditioning for Repetitive and Single Shot High Power Microwave Systems
  M. Giesselmann, T. Heeren, B. McHale, E. Kristiansen, "Power Conditioning for Repetitive and Single Shot High Power Microwave Systems", invited presentation at the 2004 Directed Energy Symposium, Rockville, Maryland, cleared for inclusion into the proceedings.
Abstract:  Not Available
+ Pulsed gas breakdown with high overvoltages in argon and air
  Crull, E.; Krompholz, H.; Neuber, A.; Hatfield, L.; IEEE Conference Record - Abstracts. The 31st IEEE International Conference on Plasma Science, 2004. ICOPS 2004. 28 June-1 July 2004 Page(s):273
Abstract:  Summary form only given. Fast gas breakdown with formative times in the sub-nanosecond regime is of interest for pulsed power switching and UWB applications. Use of coaxial transmission lines with conical sections connected to a test gap enables to apply fast voltage pulses to the gap, as well as the simultaneous measurement of voltage across and current through the gap. For small pulse amplitudes, with risetimes of 400 ps, a tip-plane geometry is used, with radii of curvature of 0.5 /spl mu/m. At pulse amplitudes of 5 kV, and macroscopic field enhancements on the order of 1000, delay times between current and voltage of less than 200 ps for pressures larger than 100 torr are observed, in both argon and dry air. Corresponding current risetimes I/(dI/dt) are less than 100 ps. Using a high voltage pulser (RADAN 303B with pulse slicer SN4, risetime 150 ps at 150 kV amplitude) enables the comparison of formative times for the tip-plane geometry with those of more homogeneous field distributions in the gap.

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+ The effect of area on pulsed breakdown in water
  Truman, K.; Mankowski, J.; Wetz, D.; Kristiansen, M.; Conference Record of the Twenty-Sixth International Power Modulator Symposium, 2004 and 2004 High-Voltage Workshop. 23-26 May 2004 Page(s):126 - 128
Abstract:  Experimental results are presented on the degree to which electrode surface area impacts the dielectric strength of water. A water gap of 4 mm was tested under pulsed conditions with a maximum electric field in excess of 1 MV/cm and a maximum current of more than 20 kA. Stainless steel electrodes with a Bruce profile were used to generate a uniform electric field across the water gap. The profile of the electrodes enabled effective areas ranging from 0.5 cm/sup 2/ to 75 cm/sup 2/ while minimizing the change in capacitance of the water gap. Conclusions are made as to the effect electrode surface area has on the holdoff voltage and holdoff time of water dielectric systems.

[PDF]

+ The relevancy of environmental parameter space for electrical insulation design in aerospace vehicles
  “The relevancy of environmental parameter space for electrical insulation design in aerospace vehicles”, D. L. Schweikart, J.C. Horwath, L.C. Walko, L.L. Hatfield, H. G. Krompholz, 2004 Power Modulator Conference, San Francisco, CA, May 23-26, 2004
Abstract:  Not Available
+ Unipolar Surface Flashover
  J. Krile, A. Neuber, H. Krompholz, J. Dickens, "Unipolar Surface Flashover," presented at the 46th Annual Meeting of the Division of Plasma Physics November 15-19, 2004, Savannah, GA, Meeting ID: DPP04APS
Abstract:  Not Available
+ Voltage-current characteristic of transformer oil under high electrical stress
  Butcher, M.; Neuber, A.; Krompholz, H.; Dickens, J.; IEEE Conference Record - Abstracts. The 31st IEEE International Conference on Plasma Science, 2004. ICOPS 2004. 28 June-1 July 2004 Page(s):258
Abstract:  Summary form only given. The scattering cross-sections, transport coefficients, and details of the breakdown mechanism needed for describing current conduction in transformer oil at high applied voltages are virtually unknown. This makes it extremely difficult, if not impossible, to properly model electrical breakdown in oil. To address this issue, we have measured the V-I characteristic of transformer oil in the point-plane geometry for /spl sim/3 mm gap widths. Three regimes can be distinguished. (1) For low voltages, V <3 kV, the relationship between voltage and current is linear, exhibiting just resistive behavior within the measurement accuracy. (2) At intermediate voltages, the dependence is linear on a Fowler-Nordheim plot. (3) Between the breakdown voltage V/sub B/ /spl sim/ 30 kV and 10 kV, the current is proportional to V/sup 2/, indicating space charge limited current. Assuming a Schottky-type emission mechanism for electrons injected into the liquid, we derive an electron mobility of /spl sim/6.0/spl times/10/sup -6/ m/sup 2//Vs, which is close to values reported in the literature before. Assuming Fowler-Nordheim emission leads to 3.8/spl times/10/sup -6/ m/sup 2//Vs. The ion mobility is believed to be more than one order of magnitude lower. At this point, it is difficult to gain any more detailed information on charge transport and possible multiplication based on simple analytical methods. Hence, we applied our numerical modeling techniques already proven in analyzing high-field phenomena in polar liquids (e.g., water), to evaluate current conduction and the breakdown process in non-polar oil. By comparing our calculations with the experimental data, we hope to characterize important transport parameters, such as the electron ionization coefficient as a function of the electric field. We also present our attempts to extract details of the field-dependent non-linear processes and electrode effects close to the breakdown regime.

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Publication Year:  2003
+ Cavity resonance effect on a coaxial vircator
  Xupeng Chen; Dickens, J.; Eun Ha Choi; Mankowski, J.; Hatfield, L.L.; Kristiansen, M.; Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 2, 15-18 June 2003 Page(s):1165 - 1168 Vol.2
Abstract:  Traditionally, the radiated microwave frequency in a coaxial vircator is considered to be determined primarily by the virtual cathode oscillation frequency and the electron reflection frequency. However, some experiments at TTU show that the interaction between the virtual cathode oscillation and the cavity is a key in determining the microwave frequency and propagating mode. Particularly, we observe that the E-beam plays an important role in the cavity formation. Some possible explanations, including a virtual cavity concept, are proposed. The cavity resonance effect on a coaxial virtual cathode oscillator has been investigated in detail. The understanding of the E-beam characteristics is critical in optimizing the design of the cylindrical diode to avoid the microwave frequency shifting and mode competition.

[PDF]

+ Compact, High Power Capacitor Charger
  M. Giesselmann, T. Heeren, T. Helle, “Compact, High Power Capacitor Charger”, Proceedings of the 2003 IEEE Pulsed Power Conference, June 15-18, 2003 Dallas, Texas, p. 707…710.
Abstract:  Not Available
+ Conductivity measurements of explosively shocked aluminum and OFHC copper used for armature material in a magnetic flux compression generator
  Hemmert, D.; Mankowski, J.; Rasty, J.; Neuber, A.; Dickens, J.; Kristiansen, M.; Digest of Technical Papers, PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 2, 15-18 June 2003 Page(s):1073 - 1076 Vol.2
Abstract:  Modeling and characterization of a magnetic flux compression generator (MFCG) requires detailed knowledge of the changes in conductivity of the MFCG materials during the shock-loading phase. In the studies reported here, a thin metallic strip is shocked with an explosively generated shock wave produced from a charge of composition C-4. The shock wave is intended to simulate the shock wave and pressures produced in MFCG research currently being conducted at Texas Tech University. These pressures are estimated to be between 1 and 3 GPa. The experimental setup is arranged so that the shapes of the metallic strip and shock front are the same, as confirmed using optical fibers. This was to ensure that the test sample was shocked uniformly. The metallic test strip is pulsed with a 70 A current pulse during application of the shock wave. The current and voltage across the test sample are measured directly to determine the change in conductivity. Pressure measurements are conducted in separate tests under similar conditions using strain gauges. The results are then compared to results determined previously using a split Hopkinson pressure bar apparatus (SHPB).

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+ Design criteria for prevention of armature "turn-skipping" in helical magnetic flux compression generators
  Rasty, J.; Le, X.; Dickens, J.; Neuber, A.; Kristiansen, M.; Pulsed Power Conference, 2003. Digest of Technical Papers. PPC-2003. 14th IEEE International Volume 2, 15-18 June 2003 Page(s):1077 - 1080 Vol.2
Abstract:  Helical magnetic flux compression generators (MFCGs) are capable of producing ultra-high power electric pulses by trapping and compressing a seed magnetic field into a load coil via an explosive-driven armature. The efficiency of helical MFCGs is generally very low, about 10%, due to large magnetic flux losses. One of the main sources of magnetic flux loss is the "turn-skipping" phenomenon, in which the expanding armature fails to establish contact with every turn of the helical coil, resulting in magnetic flux loss in the skipped turns of the coil. The "turn-skipping" phenomenon is related to non-uniform or asymmetric expansion of the armature, as well as detonation end effects. Equations describing the "turn skipping" phenomenon are developed in terms of the eccentricity of the armature with respect to the helical coil, the armature's wall thickness variations and the length of the detonation end effect. Design criteria for prevention of "turn-skipping" are presented in order to achieve optimum MFCG performance.

[PDF]

+ Electrical Breakdown in Transformer Oil
  M. Cevallos, J. Dickens, A. Neuber H. Krompholz, “Electrical Breakdown in Transformer Oil,” Joint Fall Meeting of the Texas Sections of the APS and AAPT and Zone 13 Society of Physics Students, Lubbock, TX, Oct 2003 (abstract only published)
Abstract:  Not Available
+ Electromagnetic fields and discharges in advanced power systems
  “Electromagnetic fields and discharges in advanced power systems,”, J.F. Prewitt, R. St.John, S. Oetzel, G. Skidmore, L. Hatfield, H. Krompholz, s. Calico, S. Iden, D. Borger, J. Havey, S. Graybill, 29th IEEE International Pulsed Power Conference, Dallas, TX, June 2003,
Abstract:  Not Available
+ Experimental results of a 2 GW vircator
  Mankowski, J.J.; Choi, E.H.; Dickens, J.C.; Xupeng Chen; Kristiansen, M.; IEEE Conference Record - Abstracts. The 30th International Conference on Plasma Science, 2003. ICOPS 2003. 2-5 June 2003 Page(s):187
Abstract:  Summary form only given. Experimental findings on the coaxial virtual cathode oscillator (vircator) at Texas Tech University are reported. Recent modifications to the system include extending the pulse forming line that now provides an applied diode voltage of 600 kV for 70 nanoseconds at 60 kA. Other modifications include diode voltage, current, and radiated field diagnostics. In this initial phase of experiments, copper reflectors were installed within the diode to provide a simple means of microwave feedback to assist in the e-beam modulation. Thus far we have observed microwave peak power output with feedback reflectors as high as 2 GW corresponding to an efficiency of -6%. The mode observed at these high efficiencies is almost entirely TE/sub 11/. At lower efficiencies, both TM/sub 01/, and TE/sub 11/ modes are observed. These results suggest mode competition at lower efficiencies.

[PDF]

+ Fast, Real-Time Monitoring of AC-Alternators under heavy Transient Loading Conditions
  M. Giesselmann, B. McHale, M. Crawford, “Fast, Real-Time Monitoring of AC-Alternators under heavy Transient Loading Conditions”, Proceedings of the 2003 IEEE Pulsed Power Conference, June 15-18, 2003 Dallas, Texas, p. 711…714.
Abstract:  Not Available
+ Ferromagnetic and ferroelectric materials as seed sources for magnetic flux compressors
  Schoeneberg, N.; Walter, J.; Neuber, A.; Dickens, J.; Kristiansen, M.; Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 2, 15-18 June 2003 Page(s):1069 - 1072 Vol.2
Abstract:  permanent magnet based systems. Permanent magnets provide a larger energy-to-volume ratio given that the use of capacitors requires a power source as well as charging and firing circuitry. A recent design developed at Texas Tech University's Center for Pulsed Power and Power Electronics [S.I. Shkuratov, et al., 2002], focused on the demagnetization of a Neodymium-Iron-Boron magnet (Nd/sub 2/Fe/sub 14/B, B/sub r/= 1.23 T) by a shockwave generated from high explosives. The maximum specific energy achieved with this design was only 2.3 J/kg, which may not be sufficient for effectively seeding an FCG (fast capacitors have at least 20 J/kg). The same magnets were used with an alternative design, referred to as a strip FCG, which utilizes opposing magnets to generate initial magnetic field intensity within an air gap. The air gap exists between a central tube, filled with high explosives, and metal strips placed between the magnets a few millimeters off-axis. The detonation of the explosive causes the expansion of the central tube, subsequently compressing the flux into the strips and then into the load. The original strip FCG design [B.A. Bojko, et al., 1994] used oxide-barium magnets (B/sub r/= 0.2T), which produced an estimated specific energy of 5.27 J/kg into a low inductance load. These magnets were replaced with the Nd/sub 2/Fe/sub 14/B (B/sub r/= 1.23 T) magnets in order to achieve better performance, which will be analyzed with respect to the specific energy. In addition, a design utilizing a shocked ferroelectric material, PZT, as a seed current source is discussed. An explosively generated shock wave is passed through a ferroelectric material, generating a current that establishes the initial seed flux for an FCG. Preliminary tests of the ferroelectric sources indicate a possible theoretical specific energy of more than 11 J/kg or 25 J/dm/sup 3/. A comparison of the designs will be discussed with regard to the specific energy produced and the effectiveness of each to seed FCG's.

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+ Flashover Across a Dielectric Surface at Atmospheric Pressure
  J. Krile, A. Neuber, J. Dickens, and H. Krompholz, “Flashover Across a Dielectric Surface at Atmospheric Pressure,” Joint Fall Meeting of the Texas Sections of the APS and AAPT and Zone 13 Society of Physics Students, Lubbock, TX, Oct 2003 (abstract only published)
Abstract:  Not Available
+ High Power Microwave Breakdown of Dielectric Interfaces
  A. Neuber, “High Power Microwave Breakdown of Dielectric Interfaces,” invited talk at the Workshop on High Gradient RF, Argonne, IL, Oct. 7-9, 2003.
Abstract:  Not Available
+ Investigation of Pulse Power Thyristor Thermal Variations
  M. G. Hoffman, J. C. Dickens, and M. G. Giesselmann “Investigation of Pulse Power Thyristor Thermal Variations”, Proceedings of the 2003 IEEE Pulsed Power Conference, June 15-18, 2003 Dallas, Texas, p. 143…145.
Abstract:  Not Available
+ Marx generator using pseudospark switches
  Kuthi, A.; Alde, R.; Gundersen, M.; Neuber, A.; Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 1, 15-18 June 2003 Page(s):241 - 244 Vol.1
Abstract:  The design and preliminary operation of the major subsystems of a Marx style pulse generator using advanced pseudospark devices are presented. The bank consists of three 150 nF / 40 kV capacitors connected with three floating FS2000 type pseudospark switches. These switches can hold off 35 kV and pass up to 10 kA at repetition rates approaching 1 kHz. The expected lifetime of >200 kC and the relatively low housekeeping power of <50 W make the pseudospark switch an excellent candidate in compact Marx generator applications. Preliminary operation of the floating housekeeping units essential to the Marx generator is presented in deta

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+ Nanosecond laser-triggered microwave switch
  McQuage, M.M.; Neuber, A.A.; Dickens, J.C.; Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 1, 15-18 June 2003 Page(s):309 - 312 Vol.1
Abstract:  The design and experimental testing of a laser-triggered microwave switch with a nanosecond activation time is described. The objectives of the project include, confirming that a nanosecond to subnanosecond risetime is achievable in the X-band waveguide at 9 GHz with the laser-triggered switch and to determine the minimum laser energy necessary to obtain the fastest possible risetime. A 1 kW pulsed X-band source with a 500 ns output pulse provides the microwave power for the system. A variable power Nd:YAG laser with a maximum 450 mJ at 532 nm, 10 ns FWHM output pulse is used in conjunction with an applied high voltage pulse to trigger the microwave switch. The microwave signal is switched with the rapid formation of plasma caused by the breakdown of a gas contained by a quartz tube inserted through a section of waveguide. The centerpiece of the waveguide system is a magic tee, which controls the direction of power flow through the system. Compared to tests in air and N/sub 2/, the best results have been obtained in argon. Risetimes below 2 ns have been obtained using argon at a reduced pressure of 150 Torr and a high voltage pulse of 28 kV from a spark gap. The impact of gas pressure, applied voltage pulse and applied laser pulse on the risetime of the microwave switch are discussed.

[PDF]

+ Optical diagnostics of liquid nitrogen volume pre-breakdown events
  Butcher, M.; Neuber, A.; Krompholz, H.; Dickens, J.; Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 2, 15-18 June 2003 Page(s):1029 - 1032 Vol.2
Abstract:  An increased need for compact pulsed power systems requiring new switching technologies combined with the benefits of cryogenic properties, such as higher energy density and miniaturization, has lead to increased interest in liquid nitrogen as a switching medium. High hold off voltage, low dielectric constant, and low environmental impact are further advantages of liquid nitrogen. Characterization of breakdown is investigated using high-speed (temporal resolution < 1 ns) optical and electrical diagnostics in a coaxial system with 52 /spl Omega/ impedance. Experiments are done in self-breakdown mode in super-cooled liquid nitrogen with a temperature near 70 K. Discharge current and voltage are determined using transmission line type current sensors and capacitive voltage dividers. Discharge luminosity is measured with photomultiplier tubes (risetime/spl ap/800 ps) that are focused on the negative electrode tips and the center of the channel. Optical investigations of breakdown and pre-breakdown events on a nanosecond time scale will provide a better understanding of the fundamental physics of breakdown formation. Detailed optical and spectroscopic diagnostics combined with high-speed electrical diagnostics are aimed at clarifying the overall breakdown mechanisms, including electronic initiation and bubble formation. The breakdown initiation/development will be discussed.

[PDF]

+ Phenomenology of conduction and breakdown in transformer oil
  Butcher, M.; Cevallos, M.; Haustein, M.; Neuber, A.; Dickens, J.; Krompholz, H.; Electrical Insulation and Dielectric Phenomena, 2003. Annual Report. Conference on 2003 Page(s):301 - 304
Abstract:  In a coaxial test apparatus enabling the measurement of voltage and current at the test gap, dc conduction and breakdown in transformer oil caused by the application of dc voltages are investigated. Current measurements cover the range from 10/sup -1/ A to 1 kA, with temporal resolutions of milliseconds at the lowest current amplitudes to sub-nanoseconds for currents larger than 10/sup -4/ A. The dc current/voltage characteristic for sub-breakdown voltage amplitudes point to the injection of charge carriers, allow us to characterize the transport mechanisms, and the influence of space charges. For voltages approaching breakdown thresholds, quasi dc-currents rising from nanoamperes to microamperes are superimposed by current pulses with amplitudes of milliamperes and above, and durations of nanoseconds. The onset of these current pulses occurs up to 10 /spl mu/s before breakdown. One of these current pulses reaches a critical amplitude causing voltage breakdown and current rise to the impedance-limited value within 2 ns. Additional optical diagnostics using photomultipliers and high-speed photography with gated microchannel plates yield information on hydrodynamic processes and charge carrier amplification mechanisms associated with the current pulses and final breakdown, such as bubble formation, as well as on the development of the spark plasma finally bridging the gap.

[PDF]

+ Physical efficiency limits of inch-sized helical MFCGs
  Neuber, A.A.; Hernandez, J.-C.; Holt, T.A.; Dickens, J.C.; Kristiansen, M.; Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 1, 15-18 June 2003 Page(s):413 - 416 Vol.1
Abstract:  Helical magnetic flux compression generators (MFCG) are attractive energy sources with respect to their specific energy output. A variety of one-time use applications would benefit from small inch-sized helical generators with high specific energy output. However, it is widely accepted that the generator performance deteriorates with decreasing size. Previous experimental data have shown that the increase of the ohmic resistance of the MFCG with a reduction in size is the primary cause for the observed behavior when the initial generator inductance is held constant. We will analyze the situation in more depth and quantify how much the efficiency is determined by ohmic losses and intrinsic flux losses (flux that is left behind in the conductors and lost for compression) for different generator sizes and geometries. Our simple constant diameter MFCGs exhibit more intrinsic than ohmic losses (69% compared to 16%), while our MFCGs with tapered armatures display less intrinsic and more ohmic flux losses (13% compared to 66%), however, at increased overall efficiency. We will show experimental and calculated data and discuss the physical efficiency limits and scaling of generator performance at small sizes.

[PDF]

+ Physics of dielectric surface flashover at atmospheric pressure
  Krile, J.; Neuber, A.; Dickens, J.; Krompholz, H.; Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 1, 15-18 June 2003 Page(s):285 - 288 Vol.1
Abstract:  The limits of the applicability of DC, AC, or pulsed high voltage are determined by breakdown along insulators or insulating support structures. It is of major technical importance to predict breakdown voltages for given structures, with parameters such as geometry, material, and temporal characteristics of the applied voltage. The impact of atmospheric conditions such as humidity, pressure, temperature, and types of gas present is also important. A setup has been devised to simulate and closely monitor flashover across various gap distances and insulator geometries at atmospheric conditions at different humidities. Current, voltage, luminosity, and optical emission spectra were measured with nanosecond to subnanosecond resolution. Spatially and temporally resolved light emission data yielded quantitative information about the charge carrier amplification, the location of this amplification, and its role in the formation of streamers.

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+ Prebreakdown current behavior in DC volume breakdown in transformer oil
  Butcher, M.; Neuber, A.; Krompholz, H.; Dickens, J.; Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 1, 15-18 June 2003 Page(s):289 - 292 Vol.1
Abstract:  The phenomenology of prebreakdown events in transformer oil is investigated using high-speed electrical and optical diagnostics. Data collection using a coaxial test setup terminating into a 50/spl Omega/ load line to simulate a matched impedance system allows very fast risetimes. Transmission line type current sensors and capacitive voltage dividers with temporal resolution of 300 ps provide information about the discharge voltage and current. Steady, DC currents ranging from a few nA with less than 10 kV of applied voltage, to a few /spl mu/A prior to full breakdown are measured using an electrometer. Prebreakdown events are measured with positive and negative charging voltages with respect to ground. Light emission from the discharge is measured using a series of fast photomultiplier tubes, (risetimes 800 ps), that observe positive and negative electrode tips and center of the channel. Preliminary results on self-breakdown (breakdown voltage +44 kV) with a 2.35 mm gap show a DC (seed) current of several hundred nA with prebreakdown spikes of a few mA immediately before final breakdown. Periodicity of the current spikes combined with a general increase in magnitude prior to full breakdown has been observed. Data collection using a negative charging line, with respect to ground with enhanced field at the cathode, indicates current spikes that are typically 25 to 50% faster than spikes using a positive charging line with enhanced field at the anode. Detailed optical diagnostics along with high-speed electrical diagnostics of the pre-breakdown phase will address the physical mechanisms initiating volume breakdown.

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+ Pulsed and self electrical breakdown in biodegradable oil
  Cevallos, M.D.; Dickens, J.C.; Neuber, A.A.; Haustein, M.A.; Krompholz, H.G.; 2003. ICOPS 2003. IEEE Conference Record - Abstracts. The 30th International Conference on Plasma Science, 2-5 June 2003 Page(s):315
Abstract:  The fundamental breakdown physics of biodegradable oil is investigated with a set up that employs a cable discharge into a coaxial system with axial discharge and load line to simulate a matched terminating impedance. No discontinuities are created in the system lines when entering the discharge chamber with the implementation of a unique feed-through design. The entire impedance of the system is matched at 50 ohms. A novel design for impedance matching transitions from the discharge cable to the coaxial system to the load line allow for a sub-nanosecond response. Final results are measured on pulsed and self breakdown voltages of up to 200 kV. Self breakdown is achieved by charging the discharge cable and load line to +/- 100 kV respectively. Pulsed breakdown is achieved by charging the discharge cable and load line to +100 kV. Shorting the discharge cable generates a reflected negatively polarized pulse causing breakdown. High speed electrical and optical diagnostics have temporal resolution down to several 100 ps A complete range of information from amplitudes of 0.1 mA to 1 kA with temporal resolutions of 300 ps is achieved by using transmission line type current sensors with fast amplifiers. Capacitive voltage dividers with fast attenuators are also used. Optical measurements are performed on low level light emission using spatially resolved, fast photo-multiplier tubes (risetime of 800 ps), supplemented with high speed photography and spectroscopic investigations on a nanosecond timescale Detailed optical and spectroscopic diagnostic along with high speed electrical diagnostics will address the mechanism initiating/assisting biodegradable oil volume breakdown.

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+ Reflex-triode geometry of the virtual-cathode oscillator
  Lara, M.B.; Mankowski, J.; Dickens, J.; Kristiansen, M.; Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 2, 15-18 June 2003 Page(s):1161 - 1164 Vol.2
Abstract:  An eight-stage four-hundred kilovolt Marx bank, in connection with a 60 nanosecond pulse-forming line, is constructed and utilized as a pulsed source to power a planar version of the virtual cathode oscillator (vircator). Eight .1/spl mu/F capacitors, charged to 50 kV each, are switched in series by dry-air pressurized spark gaps. The energy from the bank charges a 23 ohm oil transmission line, breaking a peaking gap when the maximum voltage is reached, delivering a 60 ns-300 kV pulse to the diode. The design of the planar or reflex-triode geometry vircator is based upon claims of high efficiency by Didenko et al. A previously constructed TTU vircator includes a unique E-beam source, the brush cathode; in which a circular array of pins is used as an explosive field emission source to produce relatively high beam currents. The anode consists of a round wire mesh through which the E-beam passes, generating a dense cloud of negative charge known as a virtual cathode. This initial phase of testing is composed of basic operation of the entire system and baseline output power and efficiency measurements.

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+ Self electrical breakdown in biodegradable oil
  Cevallos, M.D.; Dickens, J.C.; Neuber, A.A.; Haustein, M.A.; Krompholz, H.G.; Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 2, 15-18 June 2003 Page(s):1036 - 1039 Vol.2
Abstract:  The fundamental breakdown physics of biodegradable oil is investigated with high-speed electrical and optical diagnostics with temporal resolution down to several 100 ps. The set up employs a cable discharge into a coaxial system with axial discharge and load line to simulate matched terminating impedance. A unique feed-through design creates no discontinuities in the system lines through the discharge chamber. The impedance of the system is matched at 50 ohms including a novel design for impedance matching transitions from discharge cable to coaxial system to load line allowing for a sub-nanosecond response. This paper presents results on self-breakdown with voltages of up to 60 kV. Self-breakdown is achieved by charging the discharge cable and load line to +/-30 kV respectively. Transmission line type current sensors and a capacitive voltage divider with fast amplifiers/attenuators are used in order to obtain a complete range of information from amplitudes of 0.1 mA to 1 kA with temporal resolutions of 300 ps. Optical measurements include high speed photography and shadowgraphy. Detailed optical diagnostics along with high-speed electrical diagnostics will address the mechanism initiating/assisting biodegradable oil volume breakdown.

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+ Short pulse electric field sterilization of liquid media
  Wetz, D.; Truman, K.; Dickens, J.; Mankowski, J.; Neuber, A.; Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 2, 15-18 June 2003 Page(s):1124 - 1127 Vol.2
Abstract:  In recent years, researchers have investigated methods of liquid sterilization by applying pulsed high electric fields with some degree of success. The mechanism by which microorganisms are damaged has been shown to be a function of the local electric field and exposure time while independent from thermal and electrolytic effects from the applied pulse. Most published experiments have employed electrical pulses of 10's of kV and microsecond long pulse lengths. We are employing electrical pulses in the 100's of kV range with 100 nanosecond long pulse lengths. This type pulse should be more effective at killing microorganisms and minimize energy losses due to thermal processes in the liquid media.

[PDF]

+ Single-Shot and Overstressing of High Voltage Capacitors for Compact Arkadiev-Marx Genertor
  "Single-Shot and Overstressing of High Voltage Capacitors for Compact Arkadiev-Marx Genertor", Proc.14th IEEE International Pulsed Power Conference, Dallas, TX, June 16-19, 2003 p. 723 (with S. Shkuratov, E. Talantsev, and J. Dickens).
Abstract:  Not Available
+ Small sized MFCG for driving a high impedance load
  Hernandez, J.-C.; Neuber, A.A.; Dickens, J.C.; Kristiansen, M.; Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 2, 15-18 June 2003 Page(s):1065 - 1068 Vol.2
Abstract:  End-initiated small volume magnetic flux compression generators (MFCG) have at least one order of magnitude higher energy density (by weight or volume) than capacitive energy storage with similar discharge time characteristics. Since the prime energy is built into the MFCG in form of HE, the capacitor looses even more ground if the necessary prime energy source and the charging supply are included in the weight/volume balance. However, simple MFCGs with a single helix produce high output energy only into low inductance loads, thus producing several 100 kA of current at a voltage level of only a few 10 kV. Many pulsed power devices require less current but a considerably higher voltage level. Two approaches for achieving a higher output voltage level, both utilizing two staged MFCGs, have been reported in the open literature. The first employs a more traditional transformer coupling; the second relies on a dynamic transformer or flux-trapping scheme. Although the traditional transformer coupling has theoretically the better efficiency, we chose the latter approach for our generator design, mostly since it requires a smaller number of components. Our generator has a total length of 250 mm, a helix inner diameter of 51 mm, and is wound with Teflon insulated stranded wire of different sizes in the range from AWG 12 to AWG 22. We have presently achieved an energy gain of /spl sim/ 8 and will discuss the generator performance based on experimental current/voltage waveforms.

[PDF]

+ Smart Utility Interface for Photo-Voltaic Converters
  M. Giesselmann, A. Dusang, “Smart Utility Interface for Photo-Voltaic Converters”, Proceedings of the 1st International Energy Conversion Engineering Conference (IECEC), AIAA Paper 2003-6112, Renaissance Portsmouth Hotel, Portsmouth, Virginia, 17 - 21 Aug 2003.
Abstract:  Not Available
+ Space Charge Limited Current for a 1-D Cylindrical Diode
  "Space Charge Limited Current for a 1-D Cylindrical Diode", Proc. 14th IEEE International Pulsed Power Conference, Dallas, TX, June 16-19, 2003 p. 467 (with X. Chen, J. Dickens, E. Choi).
Abstract:  Not Available
+ Sub-nanosecond point-plane gas breakdown in conical shaped spark gap
  “Sub-nanosecond point-plane gas breakdown in conical shaped spark gap”, J. Spears, H. Krompholz, L.L. Hatfield, 29th IEEE International Pulsed Power Conference, Dallas, TX, June 2003
Abstract:  Not Available
+ Surface flashover across ceramic disks in vacuum at cryogenic temperatures
  Keene, H.; Dickens, J.; Neuber, A.; Krompholz, H.; Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference, 2003. Volume 1, 15-18 June 2003 Page(s):305 - 308 Vol.1
Abstract:  As superconducting technology becomes more viable in the marketplace, especially in high power applications, the need for a well researched high thermal conductivity electrical insulator is needed. The electrical failure mode for these types of insulators is often surface flashover at subatmospheric temperature and pressure. Testing of two such insulators, aluminum nitride and aluminum oxide, for this failure mode is done for two differing electrode geometries. In addition three coats of GE 7031 dielectric varnish are applied to the exposed parts of the insulator for comparison testing with nonvarnished samples. In general the testing shows an increasing breakdown voltage trend with decreasing temperature. These results indicate a temperature related dependence of the secondary electron emission and electron induced outgassing, which is a component in the process of surface flashover. The addition of the varnish results in a lowered breakdown voltage. The research also covers the effect of electrode conditioning, and presents optical diagnostics of the gas species involved during breakdown.

[PDF]

Publication Year:  2002
+ All-Explosive Pulsed Power Generator System
  A. Neuber, S. Shkuratov, E. Talantsev, J. Walter, T. Holt, J. Dickens, and M. Kristiansen, “All-Explosive Pulsed Power Generator System,” at the Ninth International Conference on Megagauss Magnetic Field Generation and Related Topics, Moscow – St. Petersburg, July 7-14, 2002.
Abstract:  Not Available
+ Dependence of Flux Losses on MCG Helix Geometry
  A. Neuber, T. Holt, J. Hernandez, J. Dickens, and M. Kristiansen, “Dependence of Flux Losses on MCG Helix Geometry,” presented at the 14th International Conference on High-Power Particle Beams, Albuquerque, NM, June 23 - 28, 2002.
Abstract:  Not Available
+ Electric breakdown in liquid nitrogen
  Krompholz, H.; Neuber, A.; Haustein, M.; Dickens, J.; Proceedings of 2002 IEEE 14th International Conference on Dielectric Liquids, 2002. ICDL 2002. 7-12 July 2002 Page(s):167 - 170
Abstract:  The phenomenology of breakdown in liquid nitrogen is investigated with high-speed electrical and optical diagnostics (temporal resolution down to several 100 ps). The discharge apparatus uses a cable discharge into a coaxial system with axial discharge, and a load line to simulate a matched terminating impedance. Main experiments are done in self-breakdown mode in supercooled liquid nitrogen. Transmission line type current sensors and capacitive voltage dividers with fast amplifiers/attenuators cover an amplitude range of 0.1 mA to 1 kA with a time resolution of 300 ps, providing complete information about discharge voltage and current. The light emission is measured with fast photomultiplier tubes (risetime 800 ps), and these optical measurements will be supplemented by high-speed photography and spectroscopic investigations on a nanosecond time scale. First results on self-breakdown with a gap width of 1 mm and electrodes with 5 mm radius of curvature (breakdown voltage 42 kV) show a three-phase development: the current rises from an unknown level to several mA during 2 ns, stays approximately constant for 100 ns with superimposed ns-duration spikes, and shows a final exponential rise to the full impedance limited current amplitude during several nanoseconds. Detailed optical and spectroscopic diagnostics along with the high-speed electrical diagnostics will in particular address the physical mechanisms initiating/assisting the liquid nitrogen volume breakdown, such as bubble formation during the pre-breakdown phase.

[PDF]

+ Explosive-Driven Generation of Transient Antennas
  A. Neuber, N. Schoeneberg, J. Dickens, and M. Kristiansen, “Explosive-Driven Generation of Transient Antennas,” presented at the Ninth International Conference on Megagauss Magnetic Field Generation and Related Topics, Moscow – St. Petersburg, July 7-14, 2002.
Abstract:  Not Available
+ Fast dielectric volume breakdown in liquid nitrogen
  Neuber, A.; Krompholz, H.; Haustein, M.; Dickens, J.; IEEE Conference Record - Abstracts. The 29th IEEE International Conference on Plasma Science, 2002. ICOPS 2002. 26-30 May 2002 Page(s):196
Abstract:  Summary form only given, as follows. Miniaturization of electrical components along with growing superconductor technology requires a better understanding of the phenomenology of breakdown in liquid nitrogen. It is known that the time delay between breakdown-onset and final impedance-limited arc current can occur within a few nanoseconds. For a temporal resolution down to several 100 ps, a discharge apparatus was built and tested that uses a cable discharge into a coaxial system with axial discharge, and a load line to simulate a matched terminating impedance. Main experiments are done in self-breakdown mode in supercooled liquid nitrogen, pulsed breakdown at high over-voltages in standard electrode geometry is investigated as well. Transmission line type current sensors and capacitive voltage dividers with fast amplifiers/attenuators cover an amplitude range of 0.1 mA to 1 kA with a time resolution of 300 ps, providing complete information about discharge voltage and current. The light emission is measured with fast photomultiplier tubes (risetime 800 ps), and these optical measurements will be supplemented by high-speed photography and spectroscopic investigations on a nanosecond time scale. Preliminary results on self-breakdown in the surface flashover mode with a gap width of 2 mm and electrodes with 5 mm radius of curvature (breakdown voltage /spl sim/ 60 kV) show a three-phase development: the current rises from an unknown level to several mA during 2 ns, stays approximately constant for 100 ns with superimposed ns-duration spikes, and shows a final exponential rise to the full impedance limited current amplitude during several nanoseconds. The detailed optical and spectroscopic diagnostics along with the high-speed electrical diagnostics will in particular address the physical mechanisms initiating/assisting the liquid nitrogen volume breakdown, such as bubble formation during the pre-breakdown phase.

[PDF]

+ Feasibility study of an explosively formed transient antenna
  Neuber, A.; Schoeneberg, N.; Dickens, J.; Kristiansen, M.; Conference Record of the Twenty-Fifth International Power Modulator Symposium, 2002 and 2002 High-Voltage Workshop. 30 June-3 July 2002 Page(s):374 - 377
Abstract:  The feasibility of utilizing the chemical energy stored in high explosives to generate an antenna capable of radiating for several microseconds is studied. Crucial parameters such as conductivity as a function of time, maximum achievable antenna length for given initial device volume and weight, and material dependence are assessed by sub microsecond optical and electrical diagnostics. By utilizing a rotating framing mirror camera with up to 4 Megaframes per second, which produces a color image sequence consisting of 125 frames, possible premature breakup of the transient antenna rod is measured with adequate spatial and temporal resolution, thus revealing a rod growth velocity of a few millimeters/microsecond. Electrical diagnostic, primarily aimed at the conductivity between selected points along the rod propagation, enables to make a connection with the observed behavior based on the optical diagnostics. Maintaining electrical contact at the base of the device while the rod is fully formed is crucial and will be discussed in detail.

[PDF]

+ Field enhanced microwave breakdown in gas for a plasma limiter
  Hemmert, D.; Neuber, A.; Krompholz, H.; Mankowski, J.; Saeks, D.; IEEE Conference Record - Abstracts. The 29th IEEE International Conference on Plasma Science, 2002. ICOPS 2002. 26-30 May 2002 Page(s):322
Abstract:  Summary form only given, as follows. A new type of plasma limiter is being developed capable of turnon in less than 1 nsec. The approach taken is to initiate streamer breakdown via a micron radius needle tip. Studies were conducted on breakdown with a variety of gases at pressures from 10/sup 3/ to 10/sup -2/ torr. Gases tested included dry air, neon, argon, and krypton. Studies were also conducted on dc-voltage biasing the needle and its effect on breakdown. The experimental setup uses an S-band traveling wave resonant ring (TWRR) capable of power levels up to 100 MW when coupled to a 2.85 GHz, 4 MW, magnetron. High speed diagnostics with a response on the order of 1 ns record the microwave power, luminosity, and x-rays. A high speed CCD camera with an adjustable exposure time down to 10 nsec records a snapshot of the breakdown sequence. Preliminary results exhibit a reduction in expected gas breakdown levels by over two orders of magnitude.

[PDF]

+ Geometry Impact on Flux Losses in MFCGs
  A. Neuber, T. Holt, J. Hernandez, J. Dickens, and M. Kristiansen, “Geometry Impact on Flux Losses in MFCGs,” presented at the Ninth International Conference on Megagauss Magnetic Field Generation and Related Topics, Moscow – St. Petersburg, July 7-14, 2002.
Abstract:  Not Available
+ High Voltage, Sub Nanosecond Feedthrough Design for Liquid Breakdown Studies
  M. Cevallos, J. Dickens, A. Neuber, H. Krompholz, “High Voltage, Sub Nanosecond Feedthrough Design for Liquid Breakdown Studies,” presented at the 14th International Conference on High-Power Particle Beams, Albuquerque, NM, June 23 - 28, 2002, AIP conference Proceedings, Vol. 650, p. 73-76.
Abstract:  Experiments in self-breakdown mode and pulsed breakdown at high over-voltages in standard electrode geometries are performed for liquids to gain a better understanding of their fundamental breakdown physics. Different liquids of interest include liquids such as super-cooled liquid nitrogen, oils, glycerols and water. A typical setup employs a discharge chamber with a cable discharge into a coaxial system with axial discharge, and a load line to simulate a matched terminating impedance, thus providing a sub-nanosecond response. This study is focused on the feed-through design of the coaxial cable into this type of discharge chamber, with the feed-through being the critical element with respect to maximum hold-off voltage. Diverse feedthroughs were designed and simulated using Maxwell 3-D Field Simulator Version 5. Several geometrically shaped feed-through transitions were simulated, including linearly and exponentially tapered, to minimize electrostatic fields, thus ensuring that the discharge occurs in the volume of interest and not between the inner and outer conductor at the transition from the insulation of the coaxial cable to the liquid. All feedthroughs are designed to match the incoming impedance of the coaxial cable. The size of the feedthroughs will vary from liquid to liquid in order to match the coaxial cable impedance of 50. The discharge chamber has two main ports where the feed-through will enter the chamber. Each feed-through is built through a flange that covers the two main ports. This allows the use of the same discharge chamber for various liquids by changing the flanges on the main ports to match the particular liquid. The feedthroughs were designed and built to withstand voltages of up to 200 kV. The feedthroughs are also fitted with transmission line type current sensors and capacitive voltage dividers with fast amplifiers/attenuators in order to attain a complete range of information from amplitudes of 0.1mA to 1 kA with a temporal resolution of 300 ps. ©2002 American Institute of Physics

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+ Liquid Nitrogen As Fast High Voltage Switching Medium
  J. Dickens, A. Neuber, M. Haustein, H. Krompholz, “Liquid Nitrogen As Fast High Voltage Switching Medium,” presented at the 14th International Conference on High-Power Particle Beams, Albuquerque, NM, June 23 - 28, 2002, AIP conference Proceedings, Vol. 650, p. 95-98.
Abstract:  Not Available
+ Microwave breakdown studies of He-N² mixtures in a pillbox cavity from 760 to 3040 torr
  Hemmert, D.; Neuber, A.; Dickens, J.; Conference Record of the Twenty-Fifth International Power Modulator Symposium, 2002 and 2002 High-Voltage Workshop. 30 June-3 July 2002 Page(s):232 - 235
Abstract:  Microwave breakdown of various He-N/sub 2/ mixture combinations is investigated utilizing an S-band double window pillbox cavity. The objective is to determine the best combination of the two gases to maximize the mixture's ability to cool a dielectric surface while maintaining high breakdown thresholds. Helium is known to be an excellent source to dissipate heat from a dielectric, but it also has a low microwave breakdown threshold. Nitrogen does not transport heat as well, but has a much higher breakdown threshold. The studies focused on generating a series of E-field vs pressure curves for breakdown to help identify optimum He-N/sub 2/ mixture ratios. The S-band double window pillbox has a 333 cm/sup 3/ cavity with two ports to flow the gas mixture through. The pillbox is placed in a traveling wave resonant ring (TWRR) coupled to a 2.85 GHz, 4 MW, magnetron. This combination of double window pillbox and TWRR allows for testing power levels up to 40 MW. High speed diagnostics are used to measure the incident/reflected power and discharge luminosity. Coupled mass flow controllers maintain the gas mixture ratio and continuous gas flow through the cavity. Investigations can be conducted with single or multiple pulsed operations. Results ranged from a minimum of 5 MW for pure helium at 760 torr, to greater than 40 MW for pure nitrogen at 3040 torr.

[PDF]

+ Nanosecond pulsed breakdown for point-plane geometries at moderate voltage
  Nanosecond pulsed breakdown for point-plane geometries at moderate voltage”, H. Krompholz, L. Hatfield, M. Haustein, J. Spears, M. Kristiansen, AMEREM 2002, Annapolis, Md, June 2002
Abstract:  Not Available
+ Rapid Capacitor Charger
  M. Giesselmann, T. Heeren, “Rapid Capacitor Charger”, Proceedings of the 2002 Power Modulator Conference & High Voltage Workshop, Hollywood, California, June 30 – July 03, 2002.
Abstract:  Not Available
+ Rapid Capacitor Charger for Compact Marx Generators
  M. Giesselmann and T. Heeren, “Rapid Capacitor Charger for Compact Marx Generators”, Proceedings of the 2002 SAE Power Systems Conference, October 29-31, 2002, Coral Springs, Fl., SAE Paper # 2002-01-3181.
Abstract:  Not Available
+ Surface Flashover Across Ceramic Disks in Vacuum at Cryogenic Temperatures
  Keene, H.; Dickens, J.; Neuber, A.; Conference Record of the Twenty-Fifth International Power Modulator Symposium, 2002 and 2002 High-Voltage Workshop. 30 June-3 July 2002 Page(s):293 - 296
Abstract:  Not Available
+ Temperature Dependence of Laser Diode Performance
  Michael G. Giesselmann, Marc R. Hallada, “Temperature Dependence of Laser Diode Performance”, Digest of the 2002 Solid State and Diode Laser Technology Review (SSDLTR) 2002, Old Town Sheraton Hotel, Albuquerque, NM, June 3-6, 2002.
Abstract:  Not Available
Publication Year:  2001
+ Advanced Modeling of an Exploding Flux Compression Generator using Lumped Element Models of Magnetic Diffusion
  M. Giesselmann, T. Heeren, A. Neuber and M. Kristiansen, “Advanced Modeling of an Exploding Flux Compression Generator using Lumped Element Models of Magnetic Diffusion”, Proceedings of the 2001 Conference on Pulsed Power and Plasma Science, Las Vegas, Nevada, June 17-22, 2001, p. 162...165.
Abstract:  Not Available
+ Advanced Modeling of Power Electronics and Motor Drives using Pspice
  M. Giesselmann, “Advanced Modeling of Power Electronics and Motor Drives using PSpice”, Tutorial for the IEEE IAS Annual Meeting in Chicago, Illinois, Sept. 30 - Oct. 04, 2001.
Abstract:  Not Available
+ Calculating stator losses in a helical MFCG
  Benton, T.; Kuo-Ta Hsieh; Stefani, F.; Neuber, A.; Kristiansen, M.; Pulsed Power Plasma Science, 2001. PPPS-2001. Digest of Technical Papers Volume 1, 17-22 June 2001 Page(s):85 - 89 vol.1
Abstract:  This paper analyzes the transient electromagnetic, thermal, and structural behavior of the stator turns in a simple helical magnetic flux compression generator (MFCG). The main objective is to quantify the losses due to Ohmic heating and flux trapping in the conductors, including the effect of armature motion and armature proximity on the current distribution. The electric current excitation used in the modeling is based on experimental data from tests on a research MFCG. The electromagnetic (EM) and thermal analyses were conducted using EMAP3D, a 3D finite element analysis (FEA) code developed at The University of Texas at Austin (UT), which has the capability to model relative motion and sliding between conductors. Structural analyses were conducted using a version of DYNA3D that allows state data from EMAP3D to be used as input. Details of the analyses include temperature dependence on electrical, thermal, and mechanical properties.

[PDF]

+ Calculation of air temperature and pressure history during the operation of a flux compression generator
  Xiaobin Le; Rasty, J.; Neuber, A.; Dickens, J.; Kristiansen, M.; Pulsed Power Plasma Science, 2001. PPPS-2001. Digest of Technical Papers Volume 2, 17-22 June 2001 Page(s):939 - 942 vol.2
Abstract:  During the operation of magnetic flux compression generators (MFCG), the gas-plasma, shocked by the rapidly expanding armature, could lead to electrical arcing across the gas between the armature and the stator at locations where physical contact between the armature and stator has not yet occurred. This will result in a loss of magnetic flux and a decrease in the electrical efficiency of the MFCG. Therefore, knowledge of the ensuing gas temperature and pressure histories is necessary for identification of loss mechanisms in an effort to optimize the efficiency of MFCGs. This paper describes the procedure for estimating the air temperature and pressure histories via finite element (FE) simulation of the armature expansion and its ensuing contact with the stator in an MFCG. First, the validity of the FE model was verified by comparing deformation contours obtained from the simulations to those obtained experimentally via high-speed photography. Utilizing the pressure history data obtained from the FE results, the air temperature was theoretically calculated. The results indicate that the air pressure and temperature in an MFCG, having a compression ratio of 1.8, could be as high as 30 MPa and 4000/spl deg/ Kelvin, respectively.

[PDF]

+ Compact Design of a 30kV Rapid Capacitor Charger
  M. Giesselmann and E. Kristiansen, “Compact Design of a 30kV Rapid Capacitor Charger”, Proceedings of the 2001 Conference on Pulsed Power and Plasma Science, Las Vegas, Nevada, June 17-22, 2001, p. 640…643.
Abstract:  Not Available
+ Compact explosive driven shock wave ferromagnetic generators
  Shkuratov, S.I.; Talantsev, E.F.; Kristiansen, M.; Dickens, J.; Hernandez, J.C.; Neuber, A.; Digest of Technical Papers, Pulsed Power Plasma Science, 2001. PPPS-2001. Volume 1, 17-22 June 2001 Page(s):158 - 161 vol.1
Abstract:  The results are presented of tests with compact, explosively driven shock wave ferromagnetic generators. The shock wave from a high explosive charge is passed along the axis of a cylindrical, hard magnet. Two types of permanent magnets were used in the experiments: rare-earth NdFeB cylinders (D = 2.5 cm, L = 1.9 cm) and hard ferrite BaFe/sub 2/O/sub 3/ cylinders (D = 2.2 cm, L = 2.5 cm). The shock wave demagnetizes the cylinder, reducing the flux from the remnant value to zero. This change in flux generates a voltage in the winding. The current generated in the loads of the generators yielded a peak of 0.75 kA. The operation of the shock wave ferromagnetic generators was analyzed by the Maxwell 3D code. An analysis is given on the specific features of pulse generation in a system like this.

[PDF]

+ Comparative Analysis of Regression and Neural Network Models for Wind Power
  Shuhui Li, Edgar O’Hair, Michael G. Giesselmann and Don C. Wunsch, “Comparative Analysis of Regression and Neural Network Models for Wind Power”, Smart Engineering System Design, edited by Drs. Dagli, Akay, Buczak, Erosy and Fernandez, American Society of Mechanical Engineers (ASME) Press.
Abstract:  Not Available
+ Conductivity measurements of MFCG armature material under shock and high strain rates utilizing a split-hopkinson pressure bar apparatus
  Hemmert, D.; Rasty, J.; Neuber, A.; Dickens, J.; Le, X.; Kristiansen, M.; Digest of Technical Papers, 2001 Pulsed Power Plasma Science, PPPS-2001. Volume 1, 17-22 June 2001 Page(s):265 - 268
Abstract:  Not Available
+ Effect of Electron-Beam Pulse Length on Microwave Efficiency of Coaxial Vircator
  "Effect of Electron-Beam Pulse Length on Microwave Efficiency of Coaxial Vircator", Proc. 13th IEEE International Pulsed Power Conference and the 28th IEEE Conference on Plasma Science, Las Vegas, NV, June 17-22, 2001 (with W. Jiang, K. Woolverton, and J. Dickens).
Abstract:  Not Available
+ Experimental and numerical investigation of armature/stator contact in magnetic flux compression generators
  Rasty, J.; Xiaobin Le; Neuber, A.; Dickens, J.; Kristiansen, M.; Digest of Technical Papers, Pulsed Power Plasma Science, 2001. PPPS-2001. Volume 1, 17-22 June 2001 Page(s):106 - 109 vol.1
Abstract:  The efficiency of a magnetic flux compression generators (MFCG) is highly dependent on the expanding characteristics of the exploding armature and the nature of contact between the armature and the surrounding stator coil. A hydrodynamic finite element (FE) model was developed to simulate the expansion characteristics of the armature and its ensuing impact with the stator. The effectiveness of the FE model to simulate the explosive behavior of the armature was qualified by comparing the numerical results with experimentally measured parameters. Specifically, the radial displacement of the armature as well as the axial velocity of the armature/stator contact point were measured experimentally and compared with numerical results showing excellent agreement between the two. The results indicated that the radial and axial velocity with which the armature impacted the stator did not change through the length of the armature. However, the results showed that the velocity with which the contact point between the armature and the stator traveled along the length of the armature decreased as the explosion process went on. As expected, the axial propagation velocity of the contact point was found to be at its highest value (2.25 X detonation velocity) at the region close to the detonation end while approaching the detonation velocity at points away from the detonation end.

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+ Experimental study of compact explosive driven shock wave ferroelectric generators
  Shkuratov, S.I.; Kristiansen, M.; Dickens, J.; Neuber, A.; Altgilbers, L.L.; Tracy, P.T.; Tkach, Y.; Digest of Technical Papers, Pulsed Power Plasma Science, 2001. PPPS-2001. Volume 2, 17-22 June 2001 Page(s):959 - 962 vol.2
Abstract:  The design of explosive driven ferroelectric generators is presented and experimental data are discussed. The active elements are lead zirconium titanate (PZT) disks with diameter D=25 mm and thicknesses H=2.5 mm and H=6 mm and PZT cylinders with D=21 mm and H=25 mm. The high explosive charge was varied from 4.2 g to 30 g. Two different ways to initiate shock waves in the active elements were used: explosively driven flyer plates and direct action of high explosives. The data presented is for the maximum power into a resistive load.

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+ Experimental study of compact explosive-driven shock wave ferroelectric generators
  Shkuratov, S.; Kristiansen, M.; Dickens, J.; Neuber, A.; Altgilbers, L.L.; Tracy, P.T.; Tkach, Y.; IEEE Conference Record - Abstracts. Pulsed Power Plasma Science, 2001.17-22 June 2001 Page(s):227
Abstract:  Summary form only given. The design of shock wave ferroelectric generators driven by high explosives is presented and experimental data are discussed. The active elements are lead zirconium titanate (PZT) disks with diameter D=25 mm and thickness L=2.5 mm, and PZT cylinders with D=21 mm and L=25 mm. The high explosive charge was varied from 4.2 g to 30 g. Two different ways to initiate shock waves in the active elements were used: explosively driven flyer plates and direct action of high explosives. The data are presented on the maximum power released in the resistive load and on the effect of the load inductance and the load capacitance on the amplitude of the pulse produced. The experimental results are discussed in comparison to numerical simulation with the commercial circuit simulator PSPICE. An analysis is given of the specific features of pulse generation in a system like this

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+ Explosive Pulsed Electric Power Generation
  "Explosive Pulsed Electric Power Generation". Proc. 13th IEEE International Pulsed Power Conference and the 28th IEEE Conference on Plasma Science, Las Vegas, NV, June 17-22, 2001 (with J. Gregor).
Abstract:  Not Available
+ Explosive-Driven Moving Magnet Generators
  "Explosive-Driven Moving Magnet Generators", Proceedings of 13th IEEE International Pulsed Power Conference, Las Vegas, Nevada, June 2001, p. 227 (with S.I. Shkuratov, M. Kristiansen, and J.C. Dickens).
Abstract:  Not Available
+ Gas breakdown in the sub-nanosecond regime with voltages below 15 kV
  Krompholz, H.; Hatfield, L.L.; Kristiansen, M.; Hemmert, D.; Short, B.; Mankowski, J.; Brown, M.; Altgilbers, L.; Digest of Technical Papers, Pulsed Power Plasma Science, 2001. PPPS-2001. Volume 1, 17-22 June 2001 Page(s):487 - 490 vol.1
Abstract:  Gaseous breakdown in the sub-nanosecond regime is of interest for fast pulsed power switching, short pulse electromagnetics and for plasma limiters to protect devices from high power microwave radiation. Previous investigations of sub-nanosecond breakdown were mainly limited to high-pressure gases or liquids, with applied voltages in excess of 100 kV. In this paper, the authors investigate possibilities to achieve sub-nanosecond breakdown at applied voltages below 7.5 kV in point-plane geometries. The setup consists of a pulser (risetime between 400 ps to 1 ns), 50-/spl Omega/ transmission line, axial needle-plane gap with outer coaxial conductor, and a 50-/spl Omega/ load line. The needle consists of tungsten and has a radius of curvature below 0.5 /spl mu/m. The constant system impedance of 50 /spl Omega/ (except in the vicinity of the gap) and a special transmission-line-type current sensors enables current and voltage measurements with a dynamic range covering several orders of magnitude, with temporal resolution down to 80 ps. For pulse amplitudes of 1.7 kV (which are doubled at the open gap before breakdown) delay times between start of the pulse and start of a measurable current flow (amplitude > several milliamperes) have a minimum of about 8 ns, at a pressure of 50 torr in argon. Voltages of 7.5 kV produce breakdowns with a delay of about 1 ns. With negative pulses applied to the tip, at an amplitude of 7.5 kV, breakdown is always observed during the rising part of the pulse, with breakdown delay times below 800 ps, at pressures between 1 and 100 torr. At lower pressure, a longer delay time (8 ns at 50 mtorr) is observed. They authors expect the breakdown mechanism to be dominated by electron field emission, but still influenced by gaseous amplification.

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+ High speed optical diagnostics of an exploding wire fuse for power conditioning of explosive flux compression generators
  Giesselmann, M.; Heeren, T.; Neuber, A.; Walter, J.; Kristiansen, M.; Digest of Technical Papers, Pulsed Power Plasma Science, 2001. PPPS-2001. Volume 1, 17-22 June 2001 Page(s):102 - 105 vol.1
Abstract:  This paper presents high-speed optical diagnostics of an exploding wire fuse, which is used in the power conditioning system for an explosive flux compression generator. The images were taken using an IMACON(R) 790 high-speed framing camera utilizing a gated image intensifier tube. For the authors' measurements, the camera was operated in the high-speed multiple frame mode, yielding 8-10 sequential, 2 dimensional pictures with 100 ns between exposures.

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+ High Voltage Testing of Capacitors
  "High Voltage Testing of Capacitors", Proceedings of 13th IEEE International Pulsed Power Conference, Las Vegas, Nevada, June 2001, p. 1563 (with S.I. Shkuratov, J.C. Dickens and E. Horrocks).
Abstract:  Not Available
+ Impact of helix geometry on MCG flux losses [magneto cumulative generators]
  Holt, T.; Neuber, A.; Dickens, J.; Kristiansen, M.; Digest of Technical Papers, Pulsed Power Plasma Science, 2001. PPPS-2001. Volume 2, 17-22 June 2001 Page(s):905 - 908 vol.2
Abstract:  Explosively driven magnetic flux compression has been the object of research for more than three decades. Recently heightened interest has been focused on the basic physical mechanisms that determine the performance of helical magneto cumulative generators (MCGs). Two single-pitch helical flux compression generators of different sizes have been tested using current-voltage probes and optical diagnostics. The main parameters used to characterize the experimental performance of the flux compression generators were the flux conservation and theoretical current gain of each type of generator. Helices with constant pitch and differing separation between wires as well as wires with different insulation thickness were tested and analyzed with respect to their flux conservation and theoretical current gain. Preliminary results show that the insulation thickness plays only a minor role for a change in flux conservation due to geometry in the range from 0.01 to 0.5 mm provided that no internal breakdown occurred. Additionally, the overall physical dimension of the generator was modified to allow for a substantial increase in initial inductance. The outer diameter of the generator armature was held constant at 1.5 inches and the coil diameter was varied from 2.6 to 3.5 inches (expansion ratio of 1.7 or 2.3, respectively). The results gained from the conservative expansion ratio of 1.7 were used as a base to compare to the generator performance at the more aggressive expansion ratio of 2.3. First results show that an expansion ratio of 2.3 produces viable results for a partially annealed Aluminum armature with a Gurney angle of approximately 15 degrees.

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+ The Current Mode of Pulsed Power Generation in Moving Magnet Systems
  "The Current Mode of Pulsed Power Generation in Moving Magnet Systems", Proceedings of 13th IEEE International Pulsed Power Conference, Las Vegas, Nevada, June 2001, p. 228 (with S.I. Shkuratov, M. Kristiansen, J.C. Dickens, and J.C. Hernandez).
Abstract:  Not Available
+ Theoretical Treatment of Explosive Driven Ferroelectric Generators
  "Theoretical Treatment of Explosive Driven Ferroelectric Generators", Proceedings of 13th IEEE International Pulsed Power Conference, Las Vegas, Nevada, June 2001, p. 231 (with L.L. Altgilbers, Y. Tkach, S.I. Shkuratov, M. Kristiansen, J.C. Dickens, P.T. Tracy).
Abstract:  Not Available
+ Thermodynamic state of the magnetic flux compression generator volume
  Neuber, A.A.; Holt, T.A.; Dickens, J.C.; Kristiansen, M.; IEEE Conference Record - Abstracts, 2001 IEEE Conference on Pulsed Power Plasma Science, 17-22 June 2001 Page(s):151
Abstract:  Summary form only given, as follows.The knowledge of the thermodynamic state of the gas trapped in a helical flux compression generator is crucial for the assessment of flux loss due to internal electrical breakdown/arcing. Besides the helix deformation and armature deceleration at extremely high current amplitudes approaching 1 MA, the thermodynamic state of the shocked and compressed gas causes problems in the prediction of the generator output current vs. time towards the end of generator operation. Such a breakdown is experimentally detected as an abrupt change in the time derivative of the current waveform and it is easily distinguished from partial turn skipping by its sharper fall and non-periodic occurrence. The thermodynamic state of the generator was measured using primarily optical emission spectroscopy. Three main stages of operation are discussed: (1) The initial stage, which can be represented by a freely expanding armature, that shows fairly low gas temperatures, possibly as low as 2,000 K. (2) The intermediate stage during 14 to 4 microseconds before generator burnout that exhibits mainly an atomic copper line transition at about 0.8 eV. (3) The last few microseconds that reveal a highly compressed gas with temperatures of about 5,000 K and pressures of about 200 bar. Most experiments were conducted in air initially at STP, some results are given for SF6 initially at one atmosphere. In order to link the thermodynamic state to the breakdown sensitivity, additionally, simple conductivity measurements were conducted in current-free flux compression generator models

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+ Transient Analysis of Copper Stator Turns in MFCG
  T. Benton, K.-T. Hsieh, F. Stefani, A. Neuber, and M. Kristiansen, “Transient Analysis of Copper Stator Turns in MFCG,“ Paper No. H.06, International Conference on Pulsed Power Applications, Gelsenkirchen, March 29-30, 2001.
Abstract:  Not Available
Publication Year:  2000
+ 3-D PIC Simulation of a Coaxial Vircator
  "3-D PIC Simulation of a Coaxial Vircator", 13th International Conference on High-Power Particle Beams, June 2000, Nagaoka, Japan (with W. Jiang, (Nagaoka University of Technology), and Jim Dickens.
Abstract:  Not Available
+ Design of a 30kV Power Supply for Rapid Capacitor Charging
  M. Giesselmann and E. Kristiansen, “Design of a 30kV Power Supply for Rapid Capacitor Charging”, Proceedings of the 24th International IEEE Power Modulator Symposium, Norfolk, Virginia, June 26 – 29, 2000.
Abstract:  Not Available
+ Design of an Ultra High Power IGBT Inverter for Rapid Capacitor Charging
  M. Giesselmann and E. Kristiansen, “Design of an Ultra High Power IGBT Inverter for Rapid Capacitor Charging”, Proceedings of the 2000 SAE Power Systems Conference, ISBN 0-7680-0646-5, October 31-November 2, San Diego, CA, p. 271…274.
Abstract:  Not Available
+ Dielectric/Gas Interface Breakdown Caused by High Power Microwave
  D. Hemmert, A. Neuber, H. Krompholz, L.L. Hatfield, and M. Kristiansen, “Dielectric/Gas Interface Breakdown Caused by High Power Microwaves," Third Directed Energy Symposium, November 1-2, 2000, Albuquerque, New Mexico.
Abstract:  Not Available
+ Effect of Blade Passing on a Wind Turbine Output
  Stephen B. Bayne and Michael G. Giesselmann, “Effect of Blade Passing on a Wind Turbine Output” Proceedings of the Intersociety Energy Conversion Engineering Conference and Exhibit (IECEC). Las Vegas, Nevada, July 24 - 28, 2000.
Abstract:  Not Available
+ Energy Balance of Shock Wave Ferromagnetic Generators
  "Energy Balance of Shock Wave Ferromagnetic Generators", Proceedings of 12th Symposium on High Current Electronics, Tomsk, Russia, Sept. 24-29, 2000 (with S.I. Shkuratov and J. Dickens).
Abstract:  Not Available
+ Evaluation of a Solid State Opening Switch (SOS) Diode Pulser for use in a Electrochemical Reactor
  M. Giesselmann, M. Kristiansen, B. Grinstead, M. Wilson “Evaluation of a Solid State Opening Switch (SOS) Diode Pulser for use in a Electrochemical Reactor”, 2000 World Conference on Industrial Applications of Electrical Energy (An extended IEEE Industry Applications Society 35th Annual Meeting), Sheraton Roma Hotel, Rome Italy, October 8-12, 2000.
Abstract:  Not Available
+ Fundamental Studies of a Helical Magnetic Flux Compression Generator
  A. Neuber, J. Dickens, M. Giesselmann, B. Freeman, J. Rasty, H. Krompholz, and M. Kristiansen: Fundamental Studies of a Helical Magnetic Flux Compression Generator. Proceedings of the 13th International Conference on High-Power Particle Beams, June 25-30, 2000, Nagaoka, Japan.
Abstract:  Not Available
+ Fundamental studies of a simple helical magnetic flux compression generator
  Neuber, A.; Dickens, J.; Giesselmann, M.; Freeman, B.; Rasty, J.; Krompholz, H.; Kristiansen, M.; IEEE Conference Record - Abstracts. The 27th IEEE International Conference on Plasma Science, 2000. ICOPS 2000. 4-7 June 2000 Page(s):276
Abstract:  Summary form only given, as follows. The design of a helical flux compression generator, driven by 150 g of high explosives, for basic studies is presented and experimental results are discussed in comparison to numerical simulations. Simulation of the electric current output with the commercial circuit simulator PSPICE shows that this generator conserves the magnetic flux ideally in the low current mode, <30 kA. At current amplitudes in excess of 100 kA heating and melting of the single wound helix wire, AWG 12, limit the current flow. The volume between armature and stator is spectroscopically probed with fiber optics and valuable insight into the state of the shocked and compressed gas is gained. The same fiber optic probes are used to measure the velocity of the armature-stator contact along the generator axis. This contact velocity is largely affected by armature end effects, mainly due to the pressure loss at the detonator end. Both gas temperature and contact velocity have been successfully simulated with LS-DYNA3D, a three dimensional finite element hydrodynamic code. The generator's magnetic field structure is briefly discussed and magnetic field probe measurements are presented

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+ Helical Flux Compression Generator for Basic Research
  A. Neuber, J. Dickens, M. Giesselmann, B. Freeman, P. Worsey, H. Krompholz, and M. Kristiansen, “Helical Flux Compression Generator for Basic Research,” 12th Symposium on High Current Electronics, September 25-29, 2000, Tomsk, Russia.
Abstract:  Not Available
+ High Power Microwave Window Breakdown under Vacuum and Atmospheric Conditions
  A. Neuber, D. Hemmert, J. Dickens, H. Krompholz, L. L. Hatfield, and M. Kristiansen: High Power Microwave Window Breakdown under Vacuum and Atmospheric Conditions. Proceedings of the SPIE conference, vol. 4031, pp. 90-98, Aerosense 2000, 24-28 April 2000, Orlando Florida.
Abstract:  Not Available
+ High-Power Microwave Generation by a Coaxial Vircator
  "High-Power Microwave Generation by a Coaxial Vircator", 13th International Conference on High-Power Particle Beams, June 2000, Nagaoka, Japan (with W. Jiang (Nagaoka University of Technology), and Jim Dickens).
Abstract:  Not Available
+ Modeling of a Compulsator and Railgun System
  Michael Giesselmann and Don Eccleshall, “Modeling of a Compulsator and Railgun System”, 10th International Electromagnetic Launch Symposium, San Francisco, California, April 25-28, 2000.
Abstract:  Not Available
+ Pressure dependence of high power microwave solid dielectric/gas interface breakdown
  Neuber, A.; Hemmert, D.; Krompholz, H.; Hatfield, L.L.; Kristiansen, M.; 2000. ICOPS 2000. IEEE Conference Record - Abstracts. The 27th IEEE International Conference on Plasma Science, 4-7 June 2000 Page(s):124
Abstract:  The knowledge of the behavior of solid dielectric/gas interface breakdown caused by microwaves is crucial for developing new design methods for high power microwave windows. We investigate the physical mechanisms leading to breakdown for power levels on the order of 10 MW/cm2 at 2.85 GHz and gas pressures varying from 10-4 to 103 Torr. As an interface that is in widespread use, the focus was put on an alumina/air interface. Other gases are considered mainly for reference purposes. The high power microwaves are generated with a 4 MW magnetron having a 3.5 μs pulse width in conjunction with an S-band traveling wave resonator. This approach provides a power gain of maximum 25, sufficient to cause breakdown across the interface located in the pressure adjustable test region. The interface geometry comprises a thin ceramic alumina slab placed in the waveguide center. We ensure an almost purely tangential field and a localized breakdown by orienting the alumina slab normal to the direction of the wave propagation and making contact with two field enhancement tips placed in the middle of each waveguide broad wall

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+ Studies on a Helical Magnetic Flux Compression Generator
  A. Neuber, J. Dickens, B. Freeman, P. Worsey, H. Krompholz, and M. Kristiansen: Studies on a Helical Magnetic Flux Compression Generator. Proceedings of the SAE Power Systems Conference, October 31-November 2, 2000, San Diego, CA.
Abstract:  Not Available
+ Sub-nanosecond gas breakdown phenomena in the voltage regime below 15 kV
  H. Krompholz, L.L. Hatfield, B. Short, M. Kristiansen, “Sub-nanosecond gas breakdown phenomena in the voltage regime below 15 kV”, EUROEM 2000, Edinburgh, UK, June 2000
Abstract:  Not Available
Publication Year:  1999
+ A Multidisciplinary University Research Program on Explosive Flux Compression Generators for Directed Energy Weapons
  "A Multidisciplinary University Research Program on Explosive Flux Compression Generators for Directed Energy Weapons", Proc. 12th IEEE International Pulsed Power Conference, Monterey, CA, June 27-30, 1999 (with Bruce Freeman and Paul Worsey).
Abstract:  Not Available
+ A theory of RF window failure
  Valfells, A.; Ang, L.K.; Lau, Y.Y.; Gilgenbach, R.M.; Kishek, R.A.; Verboncoeur, J.; Neuber, A.; Krompholz, H.; Hatfield, L.L.; Plasma Science, 1999. ICOPS '99. IEEE Conference Record - Abstracts. 1999 IEEE International Conference on Plasma Science, 20-24 June 1999 Page(s):105 (Abstract only)
Abstract:  Summary form only given, as follows. We have recently developed a novel theory of multipactor discharge on a dielectric. The main results include the susceptibility diagram and the prediction that about one percent of the RF power is deposited to the dielectric surface over a wide range of conditions. In this paper, we extend the analysis to include the effects of outgassing and the subsequent ionization by the multipactoring electrons. This is an attempt to understand the final stage of dielectric failure that is initiated by multipactor. Similarities and differences in such failures, under RF and DC conditions, are explored. Analytic theory and simulation results will be presented and compared with experiments

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+ Advanced Modeling of Power Electronics and Drives using PSpice”
  M. Giesselmann, N. Mohan, “Advanced Modeling of Power Electronics and Drives using PSpice”, Tutorial for the IEEE IAS Annual Meeting in Phoenix, Arizona, Oct. 03-07, 1999.
Abstract:  Not Available
+ Characterization of the power handling capability of an S-band double disc gas cooled microwave window
  Neuber, A.; Ferguson, P.; Hendricks, K.; Hemmert, D.; Krompholz, H.; Hatfield, L.L.; Kristiansen, M.; IEEE Conference Record - Abstracts. 1999 IEEE International Conference on Plasma Science, 1999. ICOPS '99. 20-24 June 1999 Page(s):253
Abstract:  Summary form only given. The S-Band double disc microwave window comprises a rectangular waveguide to circular pillbox transition with two separate high purity, TiN coated alumina discs brazed into the pillbox. The geometrical dimensions are optimized for minimum electromagnetic wave reflection at a microwave frequency of 2.85 GHz in TE10 mode. The window is designed for power levels up to a few 100 MW with several microseconds pulse duration. Crucial for the power handling capability is the gas species and pressure of the gas flow applied for cooling the alumina discs

[PDF]

+ Design of a 30 kV Power Supply for Capacitor Charging using short Duty Burst Model
  M. Giesselmann, E. Kristiansen, “Design of a 30 kV Power Supply for Capacitor Charging using short Duty Burst Mode”, Proceedings of the 12th IEEE International Pulsed Power Conference, Monterey, California, June 27-30, 1999.
Abstract:  Not Available
+ Development of improved triggered vacuum switches
  Warren, T.; Dickens, J.; Neuber, A.; Kristiansen, M.; Frazier, G.; McNab, I.R.; Digest of Technical Papers. 12th IEEE International Pulsed Power Conference, 1999. Volume 2, 27-30 June 1999 Page(s):1264 - 1267 vol.2
Abstract:  Triggered vacuum switches (TVS) are being evaluated for use in energizing electrical loads that require rapid and efficient switching of currents on command as well as the ability to interrupt at current zero crossing. Relatively few switching alternatives are available at the high currents (>250 kA) and voltages (>10 kV) needed. The TVSs used in recent pulsed power systems have demonstrated an ability to switch significant currents and interrupt at the zero current crossing, but they are not yet as effective as desired. In particular, higher current operation and faster dielectric recovery would be beneficial. The intent of this research is to expand the understanding of the physics of the vacuum switch (especially the opening phase) and to extend the operating parameters

[PDF]

+ Energy efficiency analysis of an inductive storage system
  Kim, J.; Zhang, J.; Giesselmann, M.; Dickens, J.; Mankowski, J.; Kristiansen, M.; Digest of Technical Papers. 12th IEEE International Pulsed Power Conference, 1999. Volume 2, 27-30 June 1999 Page(s):1445 - 1448 vol.2
Abstract:  In this paper, the simulation and evaluation of energy efficiency and voltage amplification in an inductive energy storage system with resistive, capacitive and diode loads is presented. A numerical simulation with Mathcad shows that by proper reduction of the storage energy inductance and of the exploding fuse interruption time, the energy efficiency and voltage amplification can be greatly improved

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+ Energy Efficiency Analysis of an Inductive Storage System
  J. Kim, J. Zhang, M. Giesselmann, J. Dickens, J. Mankowski, M. Kristiansen, “Energy Efficiency Analysis of an Inductive Storage System”, Proceedings of the 12th IEEE International Pulsed Power Conference, Monterey, California, June 27-30, 1999.
Abstract:  Not Available
+ High voltage subnanosecond corona inception
  Mankowski, J.; Dickens, J.; Kristiansen, M.; Lehr, J.; Prather, W.; Gaudet, J.; Digest of Technical Papers. 12th IEEE International Pulsed Power Conference, 1999. Volume 2, 27-30 June 1999 Page(s):1392 - 1395 vol.2
Abstract:  Corona discharges in ultra-wideband radiating systems can have adverse effects on performance such as reflection, phase dispersion, and significant power losses. A test-bed has been assembled to experimentally observe corona created by voltage pulses similar to ultra-wideband systems. The current work involves the voltage attenuation of an incident pulse after propagation through a self-initiated corona and relative measurements of visible light emission from the photoionization produced during streamer development. Several gas dielectrics, including ambient air, N2, H2 , and SF6, were tested

[PDF]

+ High-Power Microwave Generation by Coaxial Vircator
  "High-Power Microwave Generation by Coaxial Vircator", Proc. 12th IEEE International Pulsed Power Conference, Monterey, CA, June 27-30, 1999 (with W. Jiang, K. Woolverton, J. Dickens).
Abstract:  Not Available
+ Influence of the microwave magnetic field on high power microwave window breakdown
  Hemmert, D.; Neuber, A.; Dickens, J.; Krompholz, H.; Hatfield, L.L.; Kristiansen, M.; IEEE Conference Record - Abstracts. 1999 IEEE International Conference on Plasma Science, 1999. ICOPS '99. 20-24 June 1999 Page(s):229
Abstract:  Summary form only given. Effects of the microwave magnetic field on window breakdown are investigated at the upstream and downstream side of a dielectric interface. Simple trajectory calculations of secondary electrons in an RF field show significant forward motion of electrons parallel to the microwave direction of propagation. The Lorentz-force due to the microwave magnetic field on high-energy secondary electrons might substantially influence the standard multipactor mechanism. As a result, the breakdown power level for the downstream side of a window would be higher than for the upstream side. This hypothesis was tested utilizing an S-band traveling wave resonant ring, powered by a 3 MW magnetron at 2.85 GHz, leading to a total power greater than 60 MW. Breakdown was studied on an interface geometry consisting of a thin alumina slab in the waveguide, oriented normal to the microwave propagation direction

[PDF]

+ Measurement of dynamic electrical conductivity of MFCG armature material under conditions of shock and high strain rate loading
  Rasty, J.; Xiaobin Le; Neuber, A.; Jiande Zhang; Dickens, J.; Digest of Technical Papers. 12th IEEE International Pulsed Power Conference, 1999. Volume 2, 27-30 June 1999 Page(s):708 - 711 vol.2
Abstract:  Characterization of changes in the conductivity during the shock loading process is of paramount importance in estimating the efficiency of magnetic flux compression generators (MFCG). In this study, the main emphasis was the characterization of dynamic conductivity of the armature material during the shock-loading phase. A Split Hopkinson Pressure Bar apparatus was utilized to subject as-received and annealed specimens of OFHC copper to various shock pressures. Experiments conducted to measure the resistivity of Cu specimens indicated that resistivity initially decreases, followed by a sharp increase before decreasing to a steady state value. Depending on the magnitude of the shock pressure, resistivity changes in excess of 200% were recorded

[PDF]

+ Optical Diagnostics on Helical Flux Compression Generators
  A. Neuber, J. Dickens, H. Krompholz, and M. Kristiansen: Optical Diagnostics on Helical Flux Compression Generators. 12th IEEE Int. Pulsed Power Conference, Monterey, CA (1999)
Abstract:  Not Available
+ Pulse Power Conditioning with a Transformer for an Inductive Energy Storage System
  M. Giesselmann, J. Zhang, T. Heeren, E. Kristiansen, J. Dickens, D. Castro, D. Garcia, M. Kristiansen, “Pulse Power Conditioning with a Transformer for an Inductive Energy Storage System”, Proceedings of the 12th IEEE International Pulsed Power Conference, Monterey, California, June 27-30, 1999.
Abstract:  Not Available
+ Pulsed Power Generation Using Ferromagnetic Circuits
  "Pulsed Power Generation Using Ferromagnetic Circuits", Proc. 12th IEEE International Pulsed Power Conference, Monterey, CA, June 27-30, 1999 (with S.I. Shkuratov, J. Dickens, L.L. Hatfield, and R. Martin).
Abstract:  Not Available
+ Pulsed, High Energy Testing of Resistors
  "Pulsed, High Energy Testing of Resistors", Proc. 12th IEEE International Pulsed Power Conference, Monterey, CA, June 27-30, 1999 (with S.I. Shkuratov, J. Dickens, L.L. Hatfield, and E. Horrocks).
Abstract:  Not Available
+ Simulation, Design and Test of a MOV Pulse Shaping Device for High Power Microwave Generators
  M. Giesselmann, T. Heeren, E. Kristiansen, J. Dickens, D. Castro, D. Garcia, M. Kristiansen, “Simulation, Design and Test of a MOV Pulse Shaping Device for High Power Microwave Generators”, Proceedings of the 12th IEEE International Pulsed Power Conference, Monterey, California, June 27-30, 1999.
Abstract:  Not Available
+ Surface flashover in liquid nitrogen
  Butcher, M.; Neuber, A.; Krompholz, H.; Hatfield, L.L.; 1999 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, Volume 2, 17-20 Oct. 1999 Page(s):654 - 657 vol.2
Abstract:  The use of cryogenic high voltage components to achieve higher energy densities is limited by virtually unknown insulator characteristics for cryogenic conditions. Using a fast coaxial setup, the flashover phenomena of dielectric test samples (Lexan, Alumina) immersed in liquid nitrogen are measured with optical and electrical diagnostics with nanosecond time resolution. The flashover voltage reaches a maximum of 30 kV for a 1.75 mm gap after 3 shots, and averages to about 10 kV after conditioning. Three phases in the discharge development can be distinguished: Phase 1 is a rapid current rise to the mA-regime, with several current spikes with amplitudes of less than 5 mA and durations of typically 20 ns. This phase lasts up to several 100 ns. Phase 2 is characterized by a rapid ionization with a current rise to the impedance limited value of several 100 A of phase 3 in a few nanoseconds. Waveforms of the luminosity follow the ones of the current in general. The physical mechanisms leading to this development, and the difference to the flashover phenomena in vacuum, are discussed qualitatively

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+ Surface flashover of dielectrics immersed in super-cooled liquid nitrogen
  Butcher, M.; Neuber, A.; Krompholz, H.; Hatfield, L.L.; Kristiansen, M.; Digest of Technical Papers. 12th IEEE International Pulsed Power Conference, 1999. Volume 1, 27-30 June 1999 Page(s):450 - 453 vol.1
Abstract:  In a fast coaxial setup, dielectric test sample and electrodes are immersed in super-cooled liquid nitrogen with a temperature near 68 K, and the flashover development process is characterized using fast optical and electrical diagnostics with nanosecond time resolution. The measured breakdown voltage as a function of consecutive flashover shots reaches its peak around the second flashover and declines to a constant value. This voltage is initially about 50% of the volume breakdown voltage in liquid nitrogen and drops to about 20% after the sample has been conditioned. Two materials, Lexan and alumina, were tested in the system and showed quite similar breakdown voltages, but alumina exhibited much more severe surface damage. The time resolved electrical diagnostic revealed three phases in the temporal development of the current. Phase 1 is a rapid rise to the mA regime that is probably associated with field emission. Phase 2 contains several pre-breakdown spikes with current amplitudes of less than 5 mA and duration of typically 20 nanoseconds that form and collapse over a period of tens to a couple hundred nanoseconds. Finally, Phase 3, is characterized by a rapid ionization across the surface with a current rise that covers 4 orders of magnitude in a few nanoseconds

[PDF]

+ The Design of a compact Pulse Transformer
  J. Zhang, J. Dickens, M. Giesselmann, J. Kim, E. Kristiansen, J. Mankowski, D. Garcia, M. Kristiansen, “The Design of a compact Pulse Transformer”, Proceedings of the 12th IEEE International Pulsed Power Conference, Monterey, California, June 27-30, 1999.
Abstract:  Not Available
+ The design of a compact pulse transformer
  Zhang, J.; Dickens, J.; Giesselmann, M.; Kim, J.; Kristiansen, E.; Mankowski, J.; Garcia, D.; Kristiansen, M.; Digest of Technical Papers. 12th IEEE International Pulsed Power Conference, 1999. Volume 2, 27-30 June 1999 Page(s):704 - 707 vol.2
Abstract:  To improve the pulse shape and to obtain μs order pulse duration on a diode load in an inductive energy storage system, an oil-submerged compact pulse transformer with diameter of 20 cm and length of 70 cm has been designed and tested. From theoretical calculations, the parameters with primary inductance Lp=3.4 μH, secondary inductance Ls=90 μH, and coupling coefficient K=0.772 are obtained. To prevent breakdown, a conical secondary design is adopted. Under the condition of 500 kV operation voltage, the maximum electric field in the transformer is 205 kV/cm (in oil). The axial voltage distribution on the secondary is linear. Experiments have been done to test the insulation, the mechanical force and the coupling coefficient. The test results are consistent with the design parameters

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+ The Role of Outgassing in Surface Flashover under Vacuum
  A. Neuber, J. Dickens, H. Krompholz, and M. Kristiansen: The Role of Outgassing in Surface Flashover under Vacuum. 12th IEEE Int. Pulsed Power Conference, Monterey, CA (1999), invited.
Abstract:  Not Available
+ Wind Turbine Power Estimation by Neural Networks With Kalman Filter Training on a SIMD Parallel Machine
  Shuhui Li, Donald C. Wunsch, Edgar O’Hair, Michael G. Giesselmann, “Wind Turbine Power Estimation by Neural Networks With Kalman Filter Training on a SIMD Parallel Machine”, 1999 International Joint Conference on Neural Networks, Washington, DC, July 10-16, 1999. Paper won Award for Best Presentation.
Abstract:  Not Available
Publication Year:  1998
+ Advanced Modeling of Power Electronics and Industrial Drives using PSpice for Windows
  M. Giesselmann, N. Mohan, “Advanced Modeling of Power Electronics and Industrial Drives using PSpice for Windows”, Tutorial for the IAS 1998 Annual Meeting, St Louis, Missouri, Oct. 10-15, 1998.
Abstract:  Not Available
+ Breakdown of dielectric/vacuum interfaces caused by high power microwaves
  Neuber, A.; Dickens, J.; Hemmert, D.; Krompholz, H.; Hatfield, L.L.; Kristiansen, M.; IEEE Conference Record - Abstracts. 1998 IEEE International on Plasma Science, 1998. 25th Anniversary. 1-4 June 1998 Page(s):205
Abstract:  Summary form only given. Physical mechanisms leading to microwave breakdown on dielectric/vacuum interfaces are investigated for power levels on the order of 100 MW at 2.85 GHz. A 3 MW magnetron with 3.5 μs pulse width, is coupled to an S-band traveling wave resonator which is kept at a pressure of 10-8 Torr. The investigation is focused on an interface geometry comprising a thin dielectric polymer slab in the waveguide, oriented vertical to the direction of wave propagation, and two field enhancement tips placed in the middle of each waveguide broad wall. This ensures an almost purely tangential field at the interface surface and a localized breakdown

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+ Design, Construction and Test of a 3-Phase Cryogenic Synchronous Rectifier
  Michael G. Giesselmann and Mohammad R. Haider, "Design, Construction and Test of a 3-Phase Cryogenic Synchronous Rectifier", Proceedings of the 23rd International Power Modulator Symposium, Westin Mission Hills Resort, California, June 22-25, 1998.
Abstract:  Not Available
+ Dielectric Surface Flashover in Vacuum at (100 K))
  A. Neuber, M. Butcher, H. Krompholz, and L. L. Hatfield: Dielectric Surface Flashover in Vacuum at (100 K). Proceedings of the XVIIIth International Symposium on Discharges and Insulation in Vacuum, Eindhoven (1998), Page(s): 815-818
Abstract:  Not Available
+ High voltage subnanosecond dielectric breakdown
  Mankowski, J.; Dickens, J.; Kristiansen, M.; IEEE Conference Record - Abstracts. 1998 IEEE International on Plasma Science, 1998. 25th Anniversary. 1-4 June 1998 Page(s):270
Abstract:  Summary form only given, as follows. Present day ultra-wideband (UWB) radiation sources a produce Megavolt pulses at 100's of picosecond (ps) risetimes. Empirical data on the breakdown characteristics for dielectric media at these short time lengths and high voltages are either extremely limited or non-existent. In support of the design of these UWB sources, we are investigating the breakdown characteristics, at these voltages and time lengths, of several liquids and gases. These include air, N2, H2, He, SF6, and transformer oil. The two voltage sources used in the experiments are capable of delivering 400 and 700 kV with a 400 ps risetime into an open load. These pulses are applied to the test gap area, capable of housing various gases and liquids at pressures from less than 1 to 150 atm. An empirical relationship of E-field versus breakdown time for the observed dielectrics is presented. Several other breakdown phenomena at these fast risetimes are observed. Dielectric breakdown strength dependence on polarity is investigated. Streak camera images of arc formation are captured, providing information on gap closure velocity. Also observed is the effect of ultraviolet radiation on the statistical lag time of breakdown for gas dielectrics at various pressures

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+ Simulation, Design and Construction of a Pulsed Power Supply for High Power Microwaves Using Explosively Driven Magnetic Flux Compression
  M. Kristiansen, J. Dickens, T. Hurtig, M. Giesselmann, E. Kristiansen, “Simulation, Design and Construction of a Pulsed Power Supply for High Power Microwaves Using Explosively Driven Magnetic Flux Compression”, Proceedings of the 1998 MegaGauss Conference, ISBN 982-256-016-5, Tallahassee, Florida, October 18 – 23, 1998, p. 425…428.
Abstract:  Not Available
+ Using Neural Networks to Estimate Wind Turbine Power Generation
  Shuhui Li, Donald C. Wunsch, Edgar O'Hair, Michael G. Giesselmann, "Using Neural Networks to Estimate Wind Turbine Power Generation", 1998 IEEE PES Summer Meeting, San Diego, California, July 12-16, 1998.
Abstract:  Not Available
Publication Year:  1997
+ A subnanosecond high voltage pulser for the investigation of dielectric breakdown
  Mankowski, J.; Dickens, J.; Kristiansen, M.; Pulsed Power Conference, 1997. 1997 11th IEEE International Digest of Technical Papers. Volume 1, 29 June-2 July 1997 Page(s):549 - 554 vol.1
Abstract:  A high voltage, sub-nanosecond pulser is designed and built for the purposes of investigating dielectric breakdown. The requirement for the pulser is a voltage pulse of several hundred kilovolts, pulsewidth less than a few nanoseconds, and a risetime <400 psec. This is achieved by using pulse sharpening techniques on the output of a 500 kV Marx bank. Originally designed to stimulate a lightning strike, the voltage waveform from the Marx generator has a slow decay time of tens of μsec. In order to obtain a more desirable pulse, the Marx bank is modified. By removing a lumped-element resistor a higher peak output voltage with a faster risetime can be obtained. Circuit simulations have shown the capability of achieving an 800 kV output in less than 40 nsec to a charging (pulse forming) line. The 50 Ω impedance, oil-filled, pulse forming line consists of a peaking gap and pulse slicing gap. The peaking gap decreases the risetime of the applied pulse down to about 300 psec. The pulse slicing gap is included to short the voltage applied to the delay line and test chamber

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+ Averaged and Cycle by Cycle Switching Models for Buck, Boost, Buck-Boost and Cuk Converters with common Average Switch Model
  Michael G. Giesselmann, “Averaged and Cycle by Cycle Switching Models for Buck, Boost, Buck-Boost and Cuk Converters with common Average Switch Model”, Proceedings of the 32nd Intersociety Energy Conversion Engineering Conference, IECEC-97, Honolulu, Hawaii, Jul. 27- Aug. 01, 1997.
Abstract:  Not Available
+ Computer Simulation of Coaxial Vircators
  "Computer Simulation of Coaxial Vircators", SPIE Conf., San Diego, CA, July 27-August 1, 1997, (with Kevin Woolverton and L.L. Hatfield).
Abstract:  Not Available
+ Design and Test of a High Power Inverter for a Ground Based Radar System for Theater Missile Defense
  M. Giesselmann, B. Crittenden and J. Fonseca, “Design and Test of a High Power Inverter for a Ground Based Radar System for Theater Missile Defense”, Proceedings of the 11th IEEE International Pulsed Power Conference, Baltimore, Maryland, June 29 - July 02, 1997.
Abstract:  Not Available
+ Dielectric surface flashover in vacuum at cryogenic temperature (100 K)
  Neuber, A.; Krompholz, H.; Hatfield, L.L.; 1997. IEEE 1997 Annual Report of the Conference on Electrical Insulation and Dielectric Phenomena, Volume 2, 19-22 Oct. 1997 Page(s):575 - 578
Abstract:  Recent developments in high power systems use cryogenic components, where the performance of insulators at such low temperatures is unknown. In a fast coaxial setup, electrodes and dielectric sample are cooled to less than 100 K in vacuum, and the flashover initiation processes for gap distances on the order of 1 cm are characterized using fast electrical and optical diagnostics. As reported before, two development stages can be distinguished: a first phase with slowly rising current and the presence of free electrons, with a duration of 10-50 ns, and a second stage with a fast current rise due to gaseous ionization and collision dominated electrons. First experiments comparing cooled samples and samples at room temperature do not show discernible differences for Lexan. For Alumina, however, an increase of the duration of phase 1 is observed, with a higher current amplitude at the transition from phase one to phase two. Also, the current rise in phase two is reduced. These results indicate a temperature dependence of the electron induced outgassing process which is expected to cause the transition from phase one to phase two

[PDF]

+ Diode Polarity experiments on a Coaxial Vircator
  "Diode Polarity experiments on a Coaxial Vircator", Proc. 11th IEEE Int’l. Pulsed Power Conf., Baltimore, MD, June 29-July 2, 1997 (with Kevin Woolverton and L.L. Hatfield).
Abstract:  Not Available
+ Evaluation of a Russian SOS Diode for use in a Compact Modulator System
  J. Dickens, M. Kristiansen, M. Giesselmann and J.G. Kim, "Evaluation of a Russian SOS Diode for use in a Compact Modulator System", Proceedings of the 11th IEEE International Pulsed Power Conference, Baltimore, Maryland, June 29 - July 02, 1997.
Abstract:  Not Available
+ Evaluation of a Russian SOS Diode for Use in a Compact Modulator System
  "Evaluation of a Russian SOS Diode for Use in a Compact Modulator System", Proc. 11th IEEE Int’l. Pulsed Power Conf., Baltimore, MD June 29-July 2, 1997 (with J. Dickens).
Abstract:  Not Available
+ Feasibility of Permanent Magnet Design for High Power Microwave Generators
  "Feasibility of Permanent Magnet Design for High Power Microwave Generators", Eight National Conference on High Power Microwave Technologies”, April 8-10, 1997 (with F.J. Agee and J. Gaudet).
Abstract:  Not Available
+ High voltage subnanosecond dielectric breakdow - 1997
  Mankowski, J.; Hatfield, L.; Kristiansen, M.; Agee, F.J.; Lehr, J.M.; Wells, J.; IEEE Conference Record - Abstracts., 1997 IEEE International Conference on Plasma Science, 1997. 19-22 May 1997 Page(s):317 - 318
Abstract:  Summary form only given. Present day ultra wideband radiation sources produce megavolt pulses at 100's of picosecond pulsewidths. Empirical data on the breakdown characteristics for dielectric media at these short time lengths and high voltages are either extremely limited or non-existent. In support of the design of these ultra wideband sources, we are investigating the breakdown characteristics, at these voltages and time lengths, of several liquids and gases. These include air, N2, H2, He, SF6, transformer oil, and freon-12

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+ Modeling of Power Electronics and Industrial Drives using PSpice for Windows
  M. Giesselmann, N. Mohan, W. Robbins and O. Apeldoorn, “Modeling of Power Electronics and Industrial Drives using PSpice for Windows”, Tutorial for the European Power Electronics Conference, EPE 97, Trontheim, Norway, September 1997.
Abstract:  Not Available
+ Neural Network for Wind Power Generation with Compressing Function
  Shuhui Li, Don C. Wunsch, Edgar O'Hair, Michael G. Giesselmann, "Neural Network for Wind Power Generation with Compressing Function", Proceedings of the 1997 IEEE International Conference on Neural Networks, Westin Galleria Hotel, Houston, Texas, June 9-12, 1997, p. 115…120.
Abstract:  Not Available
+ Overview of Methods and Models for Field Oriented Control and other Torque Control Strategies for 3-phase AC Machines for Automotive Electric Drives
  Michael Giesselmann, "Overview of Methods and Models for Field Oriented Control and other Torque Control Strategies for 3-phase AC Machines for Automotive Electric Drives", Second International All Electric Combat Vehicle Conference (AECV), Dearborn, Michigan, June 8-12, 1997.
Abstract:  Not Available
+ Using Neural Networks to Predict Wind Power Generation
  Shuhui Li, Edgar O’Hair and Michael G. Giesselmann, "Using Neural Networks to Predict Wind Power Generation", Proceedings of the International Solar Energy Conference, Washington, D.C., April 27-30, 1997, p. 415…420.
Abstract:  Not Available
+ Window and Cavity Breakdown caused by High Power Microwaves
  A. Neuber, J. Dickens, D. Hemmert, H. Krompholz, L. L. Hatfield, and M. Kristiansen: Window and Cavity Breakdown caused by High Power Microwaves. International Workshop on High Power Microwave Generation and Pulse Shortening, Edinburgh UK (1997)
Abstract:  Not Available
+ Window and Cavity Breakdown caused by High Power Microwaves
  A. Neuber, J. Dickens, D. Hemmert, H. Krompholz, L. L. Hatfield, and M. Kristiansen: Window and Cavity Breakdown caused by High Power Microwaves. IEEE International Conference on Plasma Science, San Diego (1997)
Abstract:  Not Available
+ Window and Cavity Breakdown caused by High Power Microwaves
  A. Neuber, J. Dickens, D. Hemmert, H. Krompholz, L. L. Hatfield, and M. Kristiansen: Window and Cavity Breakdown caused by High Power Microwaves. 11th IEEE Int. Pulsed Power Conf., Baltimore (1997)
Abstract:  Not Available
Publication Year:  1996
+ Breakdown at window interfaces caused by high power microwave fields
  J.C. Dickens, J. Elliott, L.L. Hatfield, M. Kristiansen, H. Krompholz, “Breakdown at window interfaces caused by high power microwave fields”, International Symposium on Optical Science, Engineering, and Instrumentation - SPIE’s Annual Meeting, Denver, CO, August 4-9, 1996, published in SPIE proceedings Volume 2843, “Intense Microwave Pulses IV”, pg.153
Abstract:  Not Available
+ Coaxial Vircator Source Development
  "Coaxial Vircator Source Development", 11th Int’l. Conf. On High Power Particle Beams”, Prague, Czech Republic, June 10-14, 1996 (with Kevin Woolverton and L.L. Hatfield)
Abstract:  Not Available
+ Compact Modulator Using Inductive Energy Storage and a Solid State Opening Switch
  "Compact Modulator Using Inductive Energy Storage and a Solid State Opening Switch", 1996 22nd International Power Modulator Symposium, Boca Raton, FL, June 24-27, 1996 (with James C. Dickens and John Bridges).
Abstract:  Not Available
+ Design and Construction of a Neutral Point Clamped Inverter
  M. Giesselmann and B. Crittenden, “Design and Construction of a Neutral Point Clamped Inverter”, Proceedings of the 22nd International Power Modulator Symposium, Boca Raton, Florida, June 24-27, 1996.
Abstract:  Not Available
+ Dielectric Surface Flashover with UV and Plasma Background
  F. Hegeler, H. Krompholz, L.L. Hatfield and M. Kristiansen, "Dielectric Surface Flashover with UV and Plasma Background," Symposium on “Physics, Diagnostics, and Application of Pulsed High Energy Density Plasma as an Extreme State”, Nagoya, Japan, May 1996, Japanese National Institute for Fusion Science Proceedings Series # 26 (NIFS-PROC-26, ISSN 0915-6348), pg. 104-114
Abstract:  Not Available
+ Dynamic Modeling of Switched Reluctance Machines with PSpice for Windows
  M. Giesselmann, "Dynamic Modeling of Switched Reluctance Machines with PSpice for Windows", Proceedings of the 31st Intersociety Energy Conversion Engineering Conference, IECEC-96, Washington, D.C., Aug. 11-16, 1996.
Abstract:  Not Available
+ Investigation of Power MOSFET switching at cryogenic (LN2) temperatures
  M. Giesselmann, Z. Mahmud and S. Carson, “Investigation of Power MOSFET switching at cryogenic (LN2) temperatures”, Proceedings of the 22nd International Power Modulator Symposium, Boca Raton, Florida, June 24-27, 1996.
Abstract:  Not Available
Publication Year:  1995
+ Central University Research Consortium
  "Central University Research Consortium", 10th IEEE International Pulsed Power Conference, Albuquerque, NM, July 10-13, 1995 (with Edl Schamiloglu,, Ron Gilgenbach, and Jim Benford).
Abstract:  Not Available
+ Design Considerations and Dynamic modeling of Turbo-Alternators using PSpice for Windows
  M. Giesselmann, “Design Considerations and Dynamic modeling of Turbo-Alternators using PSpice for Windows”, Proceedings of the 10th IEEE International Pulsed Power Conference, Albuquerque, New Mexico, July 3-6, 1995.
Abstract:  Not Available
+ Experimental Results from a Coaxial Virtual Cathode Oscillator
  "Experimental Results from a Coaxial Virtual Cathode Oscillator", 10th IEEE International Pulsed Power Conference, Albuquerque, NM, July 10-13, 1995 (with Mark Crawford and L.L. Hatfield).
Abstract:  Not Available
+ Insulator Development for Advanced Simulators
  "Insulator Development for Advanced Simulators", 10th IEEE International Pulsed Power Conference, Albuquerque, NM, July 10-13, 1995 (with F.K. Childers, P.S. Sincerny, S.R. Ashby, L. Mandelcorn, and M. Mendelsohn, and T.G. Engel).
Abstract:  Not Available
+ Insulator Surface Breakdown in a Simulated Low Earth Orbit Environment
  F. Hegeler, H. Krompholz, L. Hatfield, M. Kristiansen, “Insulator Surface Breakdown in a Simulated Low Earth Orbit Environment”, Proc. of the 10th IEEE Pulsed Power Conf., Albuquerque, NM, July 1995, pg. 568
Abstract:  Not Available
+ Insulator Surface Flashover with UV and Plasma Background and External Magnetic Field
  F. Hegeler, H. Krompholz, L.L. Hatfield, M. Kristiansen, “Insulator Surface Flashover with UV and Plasma Background and External Magnetic Field”, Proc. of “Conference on Electrical Insulation and Dielectric Phenomena (CEIDP)”, Virginia Beach, Va, Oct. 22-25, 1995 IEEE Catalog Nr. 95CH35842), pg. 171
Abstract:  Not Available
+ Low Frequency Inductive Heating of a Rigid Track During Track Laying
  "Low Frequency Inductive Heating of a Rigid Track During Track Laying", Conf. Record of the 1995 IEEE Industry Applications Society, 30th IAS Meeting, Orlando, FL, Oct. 8-12, 1995 (with B. Miedzinski, Z. Okraszewski, and A. Szymanski).
Abstract:  Not Available
+ Modeling of Graphite Electrode Failure in High Power Spark Gaps
  "Modeling of Graphite Electrode Failure in High Power Spark Gaps", 10th IEEE International Pulsed Power Conference, Albuquerque, NM, July 10-13, 1995 (with M. Wofford and M. Baker).
Abstract:  Not Available
+ Nanosecond Electron Beam Controlled Switching
  "Nanosecond Electron Beam Controlled Switching", 10th IEEE International Pulsed Power Conference, Albuquerque, NM, July 10-13, 1995 (with J.M. Awrach, M.C. Baker, L.L. Hatfield, S. Gangopadhyay, and K. Zinsmeyer).
Abstract:  Not Available
+ Plume Model of Hall Effect Plasma Thrusters with Temporal Consideration
  "Plume Model of Hall Effect Plasma Thrusters with Temporal Consideration", XXIV International Electric Propulsion Conference, Moscow, Russia, Sept. 19-23, 1995 (with J.C. Dickens, E. O’Hair and M. Kristiansen).
Abstract:  Not Available
+ Pulsed Electrical Breakdown in Water
  "Pulsed Electrical Breakdown in Water", 10th IEEE International Pulsed Power Conference, Albuquerque, NM, July 10-13, 1995 (with D. Lojewski and T.G. Engel).
Abstract:  Not Available
+ Pulsed Power Applications
  "Pulsed Power Applications", IEEJ/1995 International Power Electronic Conference, April 3-7, 1995, Yokohama, Japan.
Abstract:  Not Available
+ Review of various Induction Machine Models and Field Oriented Controllers for Design Center 3 (PSpice) using the Windows Interface
  M. Giesselmann, “Review of various Induction Machine Models and Field Oriented Controllers for Design Center 3 (PSpice) using the Windows Interface”, 5th International IMACS-Symposium on Systems Analysis and Simulation, Berlin, Germany, June 26-30, 1995.
Abstract:  Not Available
Publication Year:  1994
+ Compact 500 kV Pulser
  "Compact 500 kV Pulser," 21st Power Modulator Sympsoium, June 28-30, 1994, Costa Mesa, California (with T.G. Engel and J. Bridges).
Abstract:  Not Available
+ Comparison between Simulation and Experiment on a Coaxial Vircator High-Power Microwave System
  "Comparison between Simulation and Experiment on a Coaxial Vircator High-Power Microwave System", 10th International Conference on High Power Particle Beams, June 20-24, 1994, San Diego, CA (with Mark Crawford).
Abstract:  Not Available
+ Comparisons Between Simulation and Experiment on a Coaxial Vircator High-Power Microwave System
  "Comparisons Between Simulation and Experiment on a Coaxial Vircator High-Power Microwave System", 10th International Conference on High Power Particle Beams, San Diego, CA, June 20-24, 1994 (with M. Crawford and L.L. Hatfield).
Abstract:  Not Available
+ Development of Induction Motor Drives with Real Time PWM Control and Dynamic Modeling of Drive Performance
  G. Choudhury and M. Giesselmann, "Development of Induction Motor Drives with Real Time PWM Control and Dynamic Modeling of Drive Performance", IECEC-94, Monterey, California, August 7-11, 1994.
Abstract:  Not Available
+ Life Time Testing of High Power Ignitrons
  M. Giesselmann, "Life Time Testing of High Power Ignitrons", Proceedings of the 21st IEEE Power Modulator Symposium, Costa Mesa, California, June 27-30, 1994.
Abstract:  Not Available
+ Mass Erosion and Surface Voltage Holdoff Recovery of Insulators Used In A High Current, High Vacuum Surface Discharge Switch
  "Mass Erosion and Surface Voltage Holdoff Recovery of Insulators Used In A High Current, High Vacuum Surface Discharge Switch", 21st Power Modulator Symposium, June 28-30, 1994, Costa Mesa, California, (with T.G. Engel, S.L. Wester, and L.L. Hatfield).
Abstract:  Not Available
+ Mass Erosion and Surface Voltage Holdoff Recovery of Insulators Used in a High Current, High Vacuum Surface Discharge Switch
  "Mass Erosion and Surface Voltage Holdoff Recovery of Insulators Used in a High Current, High Vacuum Surface Discharge Switch", XVIth International Symposium on Discharges and Electrical Insulation in Vacuum, May 23-30, 1994, St. Petersburg/Moscow, Russia (with T.G. Engel, S.L. Wester, and L.L. Hatfield).
Abstract:  Not Available
+ Outgassing and Plasma Development in the Early Phase of Dielectric Surface Flashover in Vacuum
  G. Masten, T. Mueller, H. Krompholz, F. Hegeler, L.L. Hatfield, M. Kristiansen, "Outgassing and Plasma Development in the Early Phase of Dielectric Surface Flashover in Vacuum", Proc. of 10th International Conference on High Power Particle Beams ("Beams '94"), San Diego, CA, June 20-24, 1994
Abstract:  Not Available
+ Results from a Coaxial Vircator: Experiment and Simulation
  "Results from a Coaxial Vircator: Experiment and Simulation", Seventh National Conference on High Power Microwave Technology, Oct. 31 - Nov. 4, 1994, Monterey, CA (with Mark Crawford).
Abstract:  Not Available
+ The Early Phase of Dielectric Surface Flashover in a Simulated Low Earth Orbit Environment
  F. Hegeler, H. Krompholz, L.L. Hatfield, M. Kristiansen, "The Early Phase of Dielectric Surface Flashover in a Simulated Low Earth Orbit Environment", Proc. of 1994 Conf. on Electrical Insulation and Dielectric Phenomena (CEIDP), Arlington, TX, Oct. 1994, p. 594
Abstract:  Not Available
Publication Year:  1993
+ A Compact 500 kV Nanosecond Pulser
  "A Compact 500 kV Nanosecond Pulser", 9th IEEE Pulsed Power Conference, Albuquer­que, NM, June 21-23, 1993 (with T.G. Engel).
Abstract:  Not Available
+ Advanced Modeling of Adjustable Speed AC-Motor Drives using Pspice
  M. Giesselmann, "Advanced Modeling of Adjustable Speed AC-Motor Drives using PSpice", IMACS-TC1 '93, 4th International Conference on Computational Aspects of Electromechanical Energy Converters and Drives, July 7-9, 1993, Montreal, Quebec, Canada.
Abstract:  Not Available
+ Cathode Erosion Research on Medium to High Power Arcjet Thrusters
  "Cathode Erosion Research on Medium to High Power Arcjet Thrusters", 23rd International Electric Propulsion Conference, Seattle, WA, Sept. 13-16, 1993 (with W.J. Harris, E.A. O’Hair, and L.L. Hatfield).
Abstract:  Not Available
+ Cylindrically-Symmetric Virtual Cathode Oscillator High-Power Microwave Source
  "Cylindrically-Symmetric Virtual Cathode Oscillator High-Power Microwave Source", 9th IEEE Pulsed Power Conference, Albuquerque, NM, June 21-23, 1993 (with Mark Crawford and L.L. Hatfield).
Abstract:  Not Available
+ Development of Next Generation Intelligent Power Modules for Induction Motor Drives and Dynamic Modeling of Machine Behavior
  M. Giesselmann, C. Eldred, and D. Seitz, "Development of Next Generation Intelligent Power Modules for Induction Motor Drives and Dynamic Modeling of Machine Behavior", IECEC-93, Atlanta, Georgia, August 8-13, 1993.
Abstract:  Not Available
+ Electrode Performance of a Three Electrode, Triggered, High Energy Spark Gap Switch
  "Electrode Performance of a Three Electrode, Triggered, High Energy Spark Gap Switch", 9th IEEE Pulsed Power Conference, Albuquerque, NM, June 21-23, 1993 (with J.C. Dickens and T.G. Engel).
Abstract:  Not Available
+ Electron-Beam Controlled Switching Using Quartz and Polycrystalline ZnSe
  "Electron-Beam Controlled Switching Using Quartz and Polycrystalline ZnSe", 9th IEEE Pulsed Power Conference, Albuquerque, NM, June 21-23, 1993 (with W. Jiang, K. Zinsmeyer, M. Less and K.H. Schoenbach).
Abstract:  Not Available
+ Experimental Investigation of the Early Phase of Dielectric Surface Flashover in Vacuum
  F. Hegeler, G. Masten, G. Leiker, H. Krompholz, M. Kristiansen, "Experimental Investigation of the Early Phase of Dielectric Surface Flashover in Vacuum", Proc. 9th IEEE International Pulsed Power Conference, Albuquerque, NM, USA, 1993, p. 237
Abstract:  Not Available
+ Insulator Degradation Produced by High Current High Vacuum Surface Discharges
  "Insulator Degradation Produced by High Current High Vacuum Surface Discharges", 9th IEEE Pulsed Power Conference, Albuquerque, NM, June 21-23, 1993 (with S.L. Wester and T.G. Engel).
Abstract:  Not Available
+ Insulator Flashover under the Influence of Externally Applied Magnetic Fields
  H. Krompholz, L.L. Hatfield, "Insulator Flashover under the Influence of Externally Applied Magnetic Fields", Proc. of ICPIG XXI (International Conference on Phenomena in Ionized Gases), Bochum, Germany, September 1993 (invited), Vol. 3, p. 179
Abstract:  Not Available
+ Real-time Detection of Outgassing and Plasma Buildup during the Early Phase of Dielectric Surface Flashover
  G. Masten, T. Mueller, F. Hegeler, H. Krompholz, L.L. Hatfield, "Real-time Detection of Outgassing and Plasma Buildup during the Early Phase of Dielectric Surface Flashover", Proc. 9th IEEE International Pulsed Power Conference, Albuquerque, NM, USA, 1993, p.241
Abstract:  Not Available
+ Results of Lifetime Testing of Pulsed Power Switches Using an Electrolytic Capacitor Bank
  D.L. Loree, and M. Giesselmann, "Results of Lifetime Testing of Pulsed Power Switches Using an Electrolytic Capacitor Bank", 9th IEEE Pulsed Power Conference, Albuquerque, New Mexico, June 21-23, 1993.
Abstract:  Not Available
Publication Year:  1992
+ A Status Report on Project Hercules
  D.L. Loree, M. Kristiansen, M. Giesselmann, and D. Larson, "A Status Report on Project Hercules", Sixth Symposium on Electromagnetic Launch Technology (EML), Austin, Texas, April 28-30, 1992.
Abstract:  Not Available
+ Anode Arc Motion in High Power Arcjets
  "Anode Arc Motion in High Power Arcjets", AIAA 28th Joint Propulsion Conference and Exhibit, Nashville, TN, July 6-8, 1992, paper AIAA 92-3838 (with W.J. Harris, E.A. O'Hair, and L.L. Hatfield).
Abstract:  Not Available
+ Characterization of a Novel Single-Gap Transformer Coupled L-C Generator
  "Characterization of a Novel Single-Gap Transformer Coupled L-C Generator", 20th International Power Modulator Symposium, Myrtle Beach, SC, June 23-25, 1992. (with T.G. Engel).
Abstract:  Not Available
+ Comparison of Erosion of Various Cathode Materials in a 30 kWe Class Arcjet
  "Comparison of Erosion of Various Cathode Materials in a 30 kWe Class Arcjet", AIAA 28th Joint Propulsion Conference and Exhibit, Nashville, TN,, July 6-8, 1992, paper AIAA 92-3839 (with W.J. Harris, E.A. O'Hair, and L.L. Hatfield).
Abstract:  Not Available
+ Computer Assisted Diagnostics on a High-Power Microwave System
  "Computer Assisted Diagnostics on a High-Power Microwave System", 9th International Conference on High Power Particle Beams, Washington, DC, May 25-29, 1992 (with M. Crawford S. Calico and L. Hatfield.
Abstract:  Not Available
+ High Speed and High Resolution Diagnostics for the Early Phase of Dielectric Surface Flashover
  F. Hegeler, G. Masten, H. Krompholz, L. Hatfield, "High Speed and High Resolution Diagnostics for the Early Phase of Dielectric Surface Flashover", Proc. 1992 IEEE International Symposium on Electrical Insulation, Baltimore, MD, June 1992, p. 262
Abstract:  Not Available
+ Insulator and Electrode Mass Erosion and Surface Voltage Holdoff Recovery for Transient, High Current Surface Discharges
  "Insulator and Electrode Mass Erosion and Surface Voltage Holdoff Recovery for Transient, High Current Surface Discharges", 6th Electromagnetic Launch Technology, April 28-30, 1992, Austin, TX (with T.G. Engel and J.C. Dickens).
Abstract:  Not Available
+ Physical Model and Experimental Results of Cathode Erosion Related to Power Supply Ripple
  "Physical Model and Experimental Results of Cathode Erosion Related to Power Supply Ripple", AIAA 28th Joint Propulsion Conference and Exhibit, Nashville, TN, July 6-8, 1992, paper AIAA 92-3837 (with W.J. Harris, E.A. O'Hair, and L.L. Hatfield).
Abstract:  Not Available
+ Spark Gap Ignitor Studies on a Pulsed Power Ignitron
  D.L. Loree, M. Giesselmann, and M. Kristiansen, "Spark Gap Ignitor Studies on a Pulsed Power Ignitron", XVth International Symposium on Discharges and Electrical Insulation in Vacuum, Darmstadt, Germany, Sep. 6-10, 1992.
Abstract:  Not Available
+ The Early Phase of Dielectric Surface Flashover
  F. Hegeler, G. Masten, H. Krompholz, L. Hatfield, "The Early Phase of Dielectric Surface Flashover", Proc. of Conference on Electrical Insulation and Dielectric Phenomena, Victoria, B.C., Canada, Oct. 18-21, 1992, p. 463
Abstract:  Not Available
+ The Early Phase of Dielectric Surface Flashover in Vacuum
  F. Hegeler, G. Masten, H. Krompholz, L. Hatfield, "The Early Phase of Dielectric Surface Flashover in Vacuum", Proc. XVth International Symposium on Discharges and Electrical Insulation in Vacuum, Darmstadt, Germany, Sep. 6-10, 1992, p. 213
Abstract:  Not Available
+ Using Magnetic Pulse Shaping to Reduce Spark-Gap Losses and Electrode Erosion
  "Using Magnetic Pulse Shaping to Reduce Spark-Gap Losses and Electrode Erosion", 20th International Power Modulator Symposium, Myrtle Beach, SC, June 23-25, 1992. (with M. Wofford and M. Baker).
Abstract:  Not Available
Publication Year:  1991
+ A simple computer simulation of magnetic inhibition of dielectric surface flashover
  M. Lehr, H. Krompholz, M. Kristiansen, "A simple computer simulation of magnetic inhibition of dielectric surface flashover", Proc. Eighth IEEE International Pulsed Power Conference, San Diego, Ca., June 1991, p. 332
Abstract:  Not Available
+ A Voltage Inverter for Speed Control of 3-Phase Induction Motors
  D. Doan, M. Tanner, S. Wester, M. Giesselmann, "A Voltage Inverter for Speed Control of 3-Phase Induction Motors", 26th Annual IECEC, Boston, Massachusetts, August 4-9, 1991.
Abstract:  Not Available
+ Acoustical Resonant Behavior and V-I Curves for a 30-kWe Nitrogen Arcjet
  "Acoustical Resonant Behavior and V-I Curves for a 30-kWe Nitrogen Arcjet", AIDAA/AIAA/DGLR/JSASS 22nd International Electric Propulsion Conference, Viareggio, Italy, October 14-17, 1991 (with M. Grimes, W. Harris, E. O'Hair, L. Hatfield and M. Baker).
Abstract:  Not Available
+ Characterization and Study of Light Degradation Effects in ECR a-Si:H,Cl Films
  "Characterization and Study of Light Degradation Effects in ECR a-Si:H,Cl Films", International Conference on Stability of a-Si:H, Denver, CO, Feb. 20­23, 1991 (with C.P. Palsule, S. Gangopadhyay, C. Young, and T. Trost).
Abstract:  Not Available
+ Continuous Characteristic V-I Curves for a 30 kWe Nitrogen Arcjet
  "Continuous Characteristic V-I Curves for a 30 kWe Nitrogen Arcjet", 27th Joint Propulsion Conference and Exhibit, Sacramento, CA, June 24-27, 1991 (with William J. Harris, Montgomery Grimes, Edgar A. O'Hair, and Lynn L. Hatfield).
Abstract:  Not Available
+ Effect of Current Ripple on Cathode Erosion in 30 kWe Arcjets
  "Effect of Current Ripple on Cathode Erosion in 30 kWe Arcjets", 27th Joint Propulsion Conference and Exhibit, Sacramento, CA, June 24-27, 1991 (with William J. Harris, Montgomery Grimes, Edgar A. O'Hair, and Lynn L. Hatfield).
Abstract:  Not Available
+ Fast electrical and optical diagnostics for the early phase of dielectric surface flashover
  F. Hegeler, G. Masten, H. Krompholz, L. Hatfield, "Fast electrical and optical diagnostics for the early phase of dielectric surface flashover", Proc. Eighth IEEE International Pulsed Power Conference, San Diego, Ca., June 1991, p. 878
Abstract:  Not Available
+ High Current Electron Emitters
  "High Current Electron Emitters", International School of Plasma Physics, 469, Varenna, Italy, Villa Monastero, Sept. 9-20, 1991.
Abstract:  Not Available
+ Pulsed Microwave Breakdown of Solid Dielectric/Gas Interfaces
  "Pulsed Microwave Breakdown of Solid Dielectric/Gas Interfaces", International Conference on Phenomena in Ionized Gases, Pisa, Italy, July 8-12, 1991 (with M. Crawford, S. Calico and L. Hatfield).
Abstract:  Not Available
+ Pulsed Power Sources and Circuits for High Power Microwave Devices
  "Pulsed Power Sources and Circuits for High Power Microwave Devices", International School of Plasma Physics, 445, Varenna, Italy, Villa Monastero, Sept. 9-­20, 1991.
Abstract:  Not Available
+ Pulsed Vacuum Diode Diagnostics at the Texas Tech University High Power Microwave Facility
  M. Crawford, S. Calico, M. Kristiansen, H. Krompholz, "Pulsed Vacuum Diode Diagnostics at the Texas Tech University High Power Microwave Facility", Proc. Eighth IEEE International Pulsed Power Conference, San Diego, Ca., June 1991, p. 602
Abstract:  Not Available
+ Pulsed Vacuum Diode Diagnostics at the Texas Tech University High Power Microwave Facility
  "Pulsed Vacuum Diode Diagnostics at the Texas Tech University High Power Microwave Facility", 8th Pulsed Power Conference, San Diego, CA, June 17-19, 1991 (Mark Crawford and Steve Calico).
Abstract:  Not Available
+ Recent Advances in High Power Ignitron Development
  D.L. Loree, M. Giesselmann, M. Kristiansen, A. Shulski, R. Kihara, "Recent Advances in High Power Ignitron Development", 19th Power Modulator Symposium, June 26-28, 1990, San Diego, Ca., IEEE Transactions on Electron Devices, Vol. 30, No. 4, p. 720…725, April 1991.
Abstract:  Not Available
+ Recombination Studies of a High Current Ignitron
  D.L. Loree, M. Giesselmann, E. Loree, M. Kristiansen, and A. Shulski, "Recombination Studies of a High Current Ignitron", 8th IEEE International Pulsed Power Conference", June 15-19, 1991, San Diego, California.
Abstract:  Not Available
+ Simulation of the Low Earth Orbit for the Study of Pulsed Insulator Flashover and Degradation
  M. Mayerchak, M. Kristiansen, H. Krompholz, L.L. Hatfield, G. Leiker, C. Young, "Simulation of the Low Earth Orbit for the Study of Pulsed Insulator Flashover and Degradation", Proc. Eighth IEEE International Pulsed Power Conference, San Diego, Ca., June 1991, p. 1041
Abstract:  Not Available
+ Static Pressure Measurements in a 30 kWe Class Arcjet
  "Static Pressure Measurements in a 30 kWe Class Arcjet", 27th Joint Propulsion Conference and Exhibit, Sacramento, CA, June 24-27, 1991 (with William J. Harris, Montgomery Grimes, Edgar A. O'Hair, and Lynn L. Hatfield).
Abstract:  Not Available
+ The Erosion Performance of Graphite Electrodes in High Current, High Coulomb, Spark Gaps
  "The Erosion Performance of Graphite Electrodes in High Current, High Coulomb, Spark Gaps", 8th Pulsed Power Conference, San Diego, CA, June 17-19, 1991 (with A.L. Donaldson).
Abstract:  Not Available
Publication Year:  1990
+ Characterization of a-Si:H, Cl and a-SiC:H Films prepared by Electron Cyclotron Resonance Plasma
  "Characterization of a-Si:H, Cl and a-SiC:H Films prepared by Electron Cyclotron Resonance Plasma", Proc. Materials Research Society, Amorphous Silicon Technology - 1990, 92, 627 (with S. Gangopadhyay, T. Trost, C. Young, P. Zheng, C. Palsule and M. Pleit).
Abstract:  Not Available
+ Ignitron Research at Texas Tech University
  D.L. Loree, M. Giesselmann, and M. Kristiansen, "Ignitron Research at Texas Tech University," International Magnetic Pulse Compression Workshop, Granlibakken Conference Center, Lake Tahoe, California, Feb. 12-14, 1990.
Abstract:  Not Available
+ Magnetic Field Effects on Dielectric Surface Flashover
  M. Lehr, R. Korzekwa, H. Krompholz, M. Kristiansen, "Magnetic Field Effects on Dielectric Surface Flashover", Proc. 14th International Symposium on Discharges and Electrical Insulation in Vacuum, Santa Fe, NM, Sep. 17-20, 1990, p. 347
Abstract:  Not Available
+ Plasma Diagnostics for High Power Ignitron Development
  D.L. Loree, M. Giesselmann, M. Kristiansen and A. Shulski, "Plasma Diagnostics for High Power Ignitron Development", 5th Symposium on Electromagnetic Launch Technology (EML), April 2-5, 1990, Destin, Florida.
Abstract:  Not Available
+ Surface Discharge Switch Design: The Critical Factor
  "Surface Discharge Switch Design: The Critical Factor", Proc. 19th Power Modulator Symposium, San Diego, CA, June 26-28, 1990 (with T.G. Engel, M. Baker and L.L. Hatfield).
Abstract:  Not Available
+ The Influence of Magnetic Fields on Dielectric Surface Flashover
  R. Korzekwa, M. Lehr, H. Krompholz, M. Kristiansen, "The Influence of Magnetic Fields on Dielectric Surface Flashover", Proc. of 1990 Nineteenth Power Modulator Symposium, San Diego, Ca, June 26-28, 1990, pg. 277
Abstract:  Not Available
+ The Influence of Magnetic Fields on Dielectric Surface Flashover
  H. Krompholz, R. Korzekwa, M. Lehr, M. Kristiansen, "The Influence of Magnetic Fields on Dielectric Surface Flashover", Proc. 1990 Conference on Electrical Insulation and Dielectric Phenomena, Pocono Manor, PA, Oct. 28 - Nov. 1, 1990, p. 451
Abstract:  Not Available
+ Utilization of a Thermal Model to Predict Electrode Erosion Parameters of Engineering Importance
  "Utilization of a Thermal Model to Predict Electrode Erosion Parameters of Engineering Importance", Proc. 19th Power Modulator Symposium, San Diego, CA, June 26-28, 1990 (with A.L. Donaldson).
Abstract:  Not Available
Publication Year:  1989
+ A Single Gap Transformer Coupled L-C Generator with Resonant Frequency Compensa­tion
  "A Single Gap Transformer Coupled L-C Generator with Resonant Frequency Compensa­tion", 7th Pulsed Power Conference, Monterey, CA, June 12-14, 1989 (with B. Meyer, A. Watson, and G. Engel).
Abstract:  Not Available
+ An Assessment of Erosion Resistant Cathode Materials with Potential Application in High Power Electric Propulsion Devices
  "An Assessment of Erosion Resistant Cathode Materials with Potential Application in High Power Electric Propulsion Devices", AIAA ASME 25th Joint Propulsion Conference, Mon­terey, CA, July 10-14, 1989 (with A. Donaldson).
Abstract:  Not Available
+ Arcjet Cathode Erosion Studies
  "Arcjet Cathode Erosion Studies", AIAA/ASME 25th Joint Propulsion Conference, Mon­terey, CA, July 10-14, 1989 (with E. O'Hair, A. Donaldson, L. Hatfield, S. Harris, and S. Gardner).
Abstract:  Not Available
+ Electrode Erosion as a Function of Electrode Material in High Current, High Energy Transient Arcs
  "Electrode Erosion as a Function of Electrode Material in High Current, High Energy Transient Arcs", 7th Pulsed Power Conference, Monterey, CA, June 12­14, 1989 (with A.L. Donaldson).
Abstract:  Not Available
+ High Performance Insulator Materials for High Current Switching Applications
  "High Performance Insulator Materials for High Current Switching Applications", 7th Pulsed Power Conference, Monterey, CA, June 12-14, 1989 (with T.G. Engel, B.D. Smith, J.N. Marx, and R.D. Stevenson).
Abstract:  Not Available
+ Inhibiting Surface Flashover in Vacuum and Plasma
  L. Hatfield, H. Krompholz, "Inhibiting Surface Flashover in Vacuum and Plasma", Proc. of the 6th International Symposium on High Voltage Engineering, New Orleans, La, Aug. 1989, Vol. 2, paper 25.01, invited
Abstract:  Not Available
+ Inhibiting Surface Flashover with Magnetic Field
  R. Korzekwa, M. Lehr, H. Krompholz, M. Kristiansen, "Inhibiting Surface Flashover with Magnetic Fields", IECEC '89 (24th Intersociety Energy Conversion Conference-"International Forum on Energy Engineering", August 6-11, 1989, Washington, D.C.)
Abstract:  Not Available
+ Inhibiting Surface Flashover with Magnetic Fields
  M. Lehr, R. Korzekwa, H. Krompholz, M. Kristiansen, "Inhibiting Surface Flashover with Magnetic Fields", Proc. of the 6th International Symposium on High Voltage Engineering, New Orleans, La, Aug. 1989, Vol. 3, paper 48.09
Abstract:  Not Available
+ Inhibiting Surface Flashover with Magnetic Insulation
  M. Lehr, R. Korzekwa, H. Krompholz, M. Kristiansen, "Inhibiting Surface Flashover with Magnetic Insulation", Proc. of the 7th IEEE Pulsed Power Conference, Monterey, Ca, June 1989, p. 812
Abstract:  Not Available
+ Inhibition of Dielectric Surface Flashover with Magnetic Fields for Space Conditions
  M. Lehr, R. Korzekwa, H. Krompholz, M. Kristiansen, "Inhibition of Dielectric Surface Flashover with Magnetic Fields for Space Conditions", Proc. of the 19th International Conference on Phenomena in Ionized Gases, Belgrade, Yugoslavia, July 1989, p. 86
Abstract:  Not Available
+ Optical Study of the Effects of Anode Geometry on the Performance of an Ignitron
  J.E. Burke, D.L. Loree, M. Giesselmann, and M. Kristiansen, "Optical Study of the Effects of Anode Geometry on the Performance of an Ignitron", Proceedings of the 7th IEEE Pulsed Power Conference, Monterey, California, June 11-14, 1989.
Abstract:  Not Available
+ Preliminary Interferometric Investigations of a Demountable Ignitron
  D.L. Loree, J.E. Burke, M. Giesselmann, and M. Kristiansen, "Preliminary Interferometric Investigations of a Demountable Ignitron", Proceedings of the 7th IEEE Pulsed Power Conference, Monterey, California, June 11-14, 1989.
Abstract:  Not Available
+ Preliminary Interferometric Investigations of a Demountable Ignitron
  "Preliminary Interferometric Investigations of a Demountable Ignitron", 7th Pulsed Power Conference, Monterrey, CA, June 12-14, 1989 (with D.L. Loree, J.E. Burke, and M. Kristiansen).
Abstract:  Not Available
Publication Year:  1988
+ Axial Magnetic Field Effects on Redesigned Ignitrons Utilizing Glass Walls and Cylindrical Dielectric Inserts
  D. Adkins-Loree, M. Giesselmann, and M. Kristiansen, "Axial Magnetic Field Effects on Redesigned Ignitrons Utilizing Glass Walls and Cylindrical Dielectric Inserts", Proceedings of the 18th Power Modulator Symposium, June 20-22, 1988, Hyatt Regency, Hilton Head Island, South Carolina, p. 241...246.
Abstract:  Not Available
+ Computer Aided Teaching of Electromagnetic and Electro-mechanical Energy Conversion Devices
  J.P. Craig and M. Giesselmann, "Computer Aided Teaching of Electromagnetic and Electro-mechanical Energy Conversion Devices", 21st Frontiers of Power Conference, October 10-11, 1988, Oklahoma State University, Oklahoma City, Oklahoma.
Abstract:  Not Available
+ Dielectric strength of High Power Ignitrons in Axial Magnetic Fields
  D. Adkins-Loree, M. Giesselmann and M. Kristiansen, "Dielectric strength of High Power Ignitrons in Axial Magnetic Fields", Proceedings of the 1988 IEEE International Symposium on Electrical Insulation and Dielectric Phenomena, CEIDP, October 1988, Ottawa, Canada, p. 72...77.
Abstract:  Not Available
+ Magnetic Insulation for Dielectric Surfaces
  R. Korzekwa, M. Lehr, H. Krompholz, M. Kristiansen, "Magnetic Insulation for Dielectric Surfaces", Beams '88, 7th Int. Conference on High Power Particle Beams, Karlsruhe, FRG, July 1988, vol. 2, p. 1061
Abstract:  Not Available
+ Magnetic Insulation for Space Environment
  H. Krompholz, R. Korzekwa, M. Lehr, M. Kristiansen, "Magnetic Insulation for Space Environment" SPSE conference on Space Power and Power Conditioning, Los Angeles, Ca, January 1988, pg. 341
Abstract:  Not Available
+ Magnetic Insulation of Dielectric Surfaces for Space Environment
  R. Korzekwa, M. Lehr, H. Krompholz, M. Kristiansen, "Magnetic Insulation of Dielectric Surfaces for Space Environment", 1988 IEEE International Symposium on Electrical Insulation, Boston, Ma., June 1988, p. 50
Abstract:  Not Available
+ Methods of Increasing the Surface Flashover Potential in Vacuum
  L.L. Hatfield, G.R. Leiker, E.R Boerwinkle, H. Krompholz, R. Korzekwa, M. Lehr, M. Kristiansen, "Methods of Increasing the Surface Flashover Potential in Vacuum", 13th Symposium on Discharges and Electrical Insulation in Vacuum, Paris, France, 1988, vol. 1, p. 241 (invited)
Abstract:  Not Available
+ New Results on a Coating which Increases the Surface Flashover Potential
  "New Results on a Coating which Increases the Surface Flashover Potential", 13th Symp. on Discharges and Elec. Insulation in Vacuum, Paris, France, June, 1988 (with L.L. Hatfield, G.R. Leiker, and E.R. Boerwinkle).
Abstract:  Not Available
+ Performance of In-Situ Copper Alloys as Electrodes in High Current, High Energy Switches
  "Performance of In-Situ Copper Alloys as Electrodes in High Current, High Energy Switches," SPIE O-E/Laser Conf., IST Section (Space Power and Power Conditioning), Los Angeles, CA, Jan. 1988 (with A.L. Donaldson and F.M. Lehr).
Abstract:  Not Available
+ State-of-the-Art Insulator and Electrode Materials for Use in High Current, High Energy Switching
  "State-of-the-Art Insulator and Electrode Materials for Use in High Current, High Energy Switching", Proc. 4th Symposium on Electromagnetic Launch Tech­nology, Austin, TX, April 1988 (with A.L. Donaldson and T.G. Engel).
Abstract:  Not Available
+ Surface Breakdown of Pre-Stressed Insulators
  "Surface Breakdown of Pre-Stressed Insulators," SPIE O-E/Laser Conf., IST Section (Space Power and Power Conditioning), Los Angeles, CA, Jan. 1988 (with L.L. Hatfield, V.K. Agarwal, and E.R. Menzel).
Abstract:  Not Available
+ The Effect of Repetition Rate on Electrode Material Performance in High Current Switches
  "The Effect of Repetition Rate on Electrode Material Performance in High Current Switches," SPIE O-E/Laser Conf., IST Section (Space Power and Power Conditioning), Los Angeles, CA, Jan. 1988 (with A.L. Donaldson and B.D. Smith).
Abstract:  Not Available
+ The Effects of Axial Magnetic Fields on High Current, High Coulomb Ignitrons
  D.L. Adkins-Loree, M. Giesselmann, M. Kristiansen, "The Effects of Axial Magnetic Fields on High Current, High Coulomb Ignitrons", Fall Meeting of AAPT, APS and SPS, November 4-5, 1988, Lubbock, Texas.
Abstract:  Not Available
+ The Performance of New, Redesigned Ignitron Tubes in Axial Magnetic Fields
  D. Adkins, M. Giesselmann, and M. Kristiansen, "The Performance of New, Redesigned Ignitron Tubes in Axial Magnetic Fields", 4th Symposium on Electromagnetic Launch Technology", April 19-21, 1988, Austin, Texas.
Abstract:  Not Available
Publication Year:  1987
+ Coating Properties which Enhance the Vacuum Surface Flashover Potential of Insulators
  "Coating Properties which Enhance the Vacuum Surface Flashover Potential of Insulators," Proc. 6th IEEE Pulsed Power Conf., June 29-July 1, 1987, Arlington, VA (with G.R. Leiker, L.L. Hatfield, C. Colmenares, W.W.Hofer, and M.S. DiCapua).
Abstract:  Not Available
+ Design and Analysis of Multi-Factor Reliability Experiments for Pulsed Power Devices
  "Design and Analysis of Multi-Factor Reliability Experiments for Pulsed Power Devices," Proc. the 6th IEEE Pulsed Power Conf., June 29-July 1, 1987, Arlington, VA (with W.J. Kolarik, J.M. Davenport, and K. McCoun).
Abstract:  Not Available
+ Electrode and Insulator Materials Performance in High Energy, High Current Switching
  "Electrode and Insulator Materials Performance in High Energy, High Current Switching", Proc. Society for the Advancement of Material and Process Engineering, Oct. 13-15, 1987, Crystal City, VA (with T. Engel and A. Donaldson).
Abstract:  Not Available
+ Electrode Erosion and Insulator Damage from Moving Arc Discharge
  "Electrode Erosion and Insulator Damage from Moving Arc Discharge," Proc. 5th International Symposium on High Voltage Engineering, Braunschweig, FRG, Aug. 24-28, 1987 (with G. Engel and F.M. Lehr).
Abstract:  Not Available
+ Laser Enhanced Attachment in Diffuse Gas Discharges
  M. Giesselmann, B. Pashaie, M. Kristiansen, and G. Schaefer, "Laser Enhanced Attachment in Diffuse Gas Discharges", 1987 IEEE International Conference on Plasma Science, June 1-3, 1987, Ar­lington, Virginia.
Abstract:  Not Available
+ Methane-Attacher Mixtures in an Electron Beam Controlled Diffuse Discharge Opening Switch
  "Methane-Attacher Mixtures in an Electron Beam Controlled Diffuse Discharge Opening Switch," Proc. 6th IEEE Pulsed Power Conf., June 29-July 1, 1987, Arlington, VA (with G. Schaefer and R.A. Korzekwa).
Abstract:  Not Available
+ Moving Arc Damage to Insulator Materials
  "Moving Arc Damage to Insulator Materials, " Proc. 6th IEEE Pulsed Power Conf., June 29-July 1, 1987, Arlington, VA (with G. Engel).
Abstract:  Not Available
+ Penning Ionization Ternary Gas Mixtures for Diffuse Discharge Opening Switches
  "Penning Ionization Ternary Gas Mixtures for Diffuse Discharge Opening Switches", Proc. Fifth International Symposium on Gaseous Dielectrics, Knoxville, TN, May 1987 (with G. Schaefer, K.H. Schoenbach, and R.A. Korzekwa).
Abstract:  Not Available
+ Short Time Optical and Electrical Diagnostics of Pulsed N2 and SF6 Discharges
  M. Giesselmann, W. Pfeiffer, and J. Wolf, "Short Time Optical and Electrical Diagnostics of Pulsed N2 and SF6 Discharges", Proceedings of the 6th IEEE Pulsed Power Conference, June 29-July 1, 1987, Arlington, Virginia, p. 182...186.
Abstract:  Not Available
+ State-of-the-Art Materials for High Current Contacts
  "State-of-the-Art Materials for High Current Contacts," Proc. 1987 International Current Collector Conference, UT at Austin, Nov. 1987 (with A.L. Donaldson and F.M. Lehr).
Abstract:  Not Available
+ The Influence of Arc Motion on Electrode Erosion in High Current, High Energy Switches
  "The Influence of Arc Motion on Electrode Erosion in High Current, High Energy Switches," Proc. the 6th IEEE Pulsed Power Conf., June 29-July 1, 1987, Arlington, VA (with F.M. Lehr, B.D. Smith, A.L. Donaldson).
Abstract:  Not Available
+ The Influence of Nitrogen on Argon Based Gas Mixtures for an Electron Beam Controlled Diffuse Discharge
  "The Influence of Nitrogen on Argon Based Gas Mixtures for an Electron Beam Controlled Diffuse Discharge", Proc. 18th ICPIG, Swansea, UK, July 1987 (with R.A. Korzekwa, G. Schaefer, and K.H. Schoenbach).
Abstract:  Not Available
Publication Year:  1986
+ A Gap Distance Threshold in Electrode Erosion in High Current, High Energy Spark Gaps
  "A Gap Distance Threshold in Electrode Erosion in High Current, High Energy Spark Gaps," Proc. 17th Power Mod. Symp., Seattle, WA, June 1986 (with A.L. Donaldson, D. Garcia, and A. Watson).
Abstract:  Not Available
+ A Treatment Which Inhibits Surface Flashover in Vacuum
  "A Treatment Which Inhibits Surface Flashover in Vacuum," Proc. XIIth Int. Symp. Discharges and Electrical Insulation in Vacuum," Israel, Sept. 1986 (with L.L. Hatfield, G.R. Leiker, C. Colmenares, W.W. Hoefer, and M.S. DiCapua).
Abstract:  Not Available
+ Breakdown of Insulators in the Space Environmen
  "Breakdown of Insulators in the Space Environment," Proc. 2nd Int. Conf. Conduction and Breakdown in Solid Dielectrics," Erlangen, FRG, July 7-10, 1986 (with V.K. Agarwal and L.L. Hatfield).
Abstract:  Not Available
+ Electrode Erosion and Insulator Damage from Moving Arc Discharges
  "Electrode Erosion and Insulator Damage from Moving Arc Discharges", Proc. of the First Meeting of the Non-Nuclear Space Power Consortium at Auburn Univ., Dec. 1986 (with F.M. Lehr, and T.G. Engel).
Abstract:  Not Available
+ Electrode Erosion in High Current, High Energy Transient Arcs
  "Electrode Erosion in High Current, High Energy Transient Arcs," Proc. 3rd Symp. Electromagnetic Launch Technology, Austin, TX, Apr. 1986 (with A.L. Donaldson, A. Watson, K. Zinsmeyer, E. Kristiansen, and R. Dethlefsen).
Abstract:  Not Available
+ Electrode Erosion Resulting from High Current Transient Arcing
  "Electrode Erosion Resulting from High Current Transient Arcing," Proc. of the First Meeting of the Non-Nuclear Space Power Consortium at Auburn Univ., Dec. 1986 (with A.L. Donaldson).
Abstract:  Not Available
+ Experimental Design in Life Cycle Life Testing
  "Experimental Design in Life Cycle Life Testing," 1986 High Voltage Workshop, Fort Monmouth, NJ, Oct. 1986 (with W.J. Kolarik, J.M. Davenport, and K. McCoun).
Abstract:  Not Available
+ Insulator and Electrode Damage Resulting from High Current (500 kA) Pulses
  "Insulator and Electrode Damage Resulting from High Current (500 kA) Pulses," 4th Int. Conf. Megagauss Magnetic Field Generation and Related Topics, Santa Fe, NM, July 1986 (with P. Ranon, A.L. Donaldson and A. Watson).
Abstract:  Not Available
+ Insulator Damage from a Moving Arc in a Surface Discharge Switch
  "Insulator Damage from a Moving Arc in a Surface Discharge Switch," CEIDP, Wilmington, DE, Nov. 1986 (with P.M. Ranon, A. Watson, T.G. Engel and L.L. Hatfield).
Abstract:  Not Available
+ Insulator Damage in High Current Discharges
  "Insulator Damage in High Current Discharges," Proc. 3rd Symp. Electromagnetic Launch Technology, Austin, TX, Apr. 1986 (with P.M. Ranon, M. Lehr and L.L. Hatfield).
Abstract:  Not Available
+ Interaction of Discharge and Circuit in an Electron-Beam Controlled Diffuse Discharge Opening Switch
  "Interaction of Discharge and Circuit in an Electron-Beam Controlled Diffuse Discharge Opening Switch," Proc. BEAMS '86, Kobe, Japan, June 1986 (with G. Schaefer, K.H. Schoenbach, B.E. Strickland, R.A. Korzekwa and K.R. Rathbun).
Abstract:  Not Available
+ Mechanism of Electrode Surface Damage and Material Removal in High Current Discharges
  "Mechanism of Electrode Surface Damage and Material Removal in High Current Discharges," Proc. 3rd Symp. Electromagnetic Launch Technology, Austin, TX, Apr. 1986 (with A. Watson, A.L. Donaldson and K. Ikuta).
Abstract:  Not Available
+ Negative Differential Conductivity in an Electron Beam Controlled Diffuse Discharge for Switching Applications
  "Negative Differential Conductivity in an Electron Beam Controlled Diffuse Discharge for Switching Applications," Proc. Int. Conf. Plasma Sci. and Technol., Beijing, China, June 1986 (with G. Schaefer, K.H. Schoenbach, B.E. Strickland and R.A. Korzekwa).
Abstract:  Not Available
+ Optimization of Gas Mixtures for Electron-Beam Controlled Diffuse Discharge Opening Switches
  "Optimization of Gas Mixtures for Electron-Beam Controlled Diffuse Discharge Opening Switches," Proc. 17th Power Mod. Symp., Seattle, WA, June 1986 (with G. Schaefer, K.H. Schoenbach, and R.A. Korzekwa).
Abstract:  Not Available
+ Overview of Applications and Needs
  "Overview of Applications and Needs," and "Ranking of Diagnostic Techniques," Proc. NATO Advanced Study Inst. on Fast Electrical and Optical Measurements," M. Nijhoff, Netherlands, 1986 (with A.K. Hyder and M.F. Rose).
Abstract:  Not Available
+ Reliability Assurance in Electromagnetic Launch Technology
  "Reliability Assurance in Electromagnetic Launch Technology, Proc. 3rd Symp. Electromagnetic Launch Technology, Austin, TX, Apr. 1986 (with W.J. Kolarik and T.L. Landers).
Abstract:  Not Available
+ Selection Criteria and Accelerated Aging of Insulators for Space Applications
  "Selection Criteria and Accelerated Aging of Insulators for Space Applications," Proc. of the First Meeting of the Non-Nuclear Space Power Consortium at Auburn Univ., Dec. 1986 (with L.L. Hatfield V.K. Agarwal, W.G. Linzey, and J. Culhane).
Abstract:  Not Available
+ Slow Wave Line-Type Pulsers
  H. Krompholz, J. Cooper, J. Doggett, K. Schoenbach, G. Schaefer, "Slow Wave Line-Type Pulsers", 17th IEEE Power Modulator Symposium, Seattle, WA, June 1986, p. 207
Abstract:  Not Available
+ Voltage - Time Characteristics in SF6 and SF6 - N2 Mixtures
  M. Giesselmann, W. Pfeiffer, J. Wolf, "Voltage - Time Characteristics in SF6 and SF6 - N2 Mixtures", 1986 IEEE International Symposium on Electrical Insulation, Washington D.C., June 1986.
Abstract:  Not Available
Publication Year:  1985
+ An e-beam controlled diffuse discharge switch
  K. Schoenbach, G. Schaefer, M. Kristiansen, H. Krompholz, D. Skaggs, E. Strickland, "An e-beam controlled diffuse discharge switch", Proc. 5th IEEE Pulsed Power Conf., Arlington, VA, USA, 1985, p. 640
Abstract:  Not Available
+ An Electron-beam Controlled Diffuse Discharge Switch
  G. Schaefer, K. Schoenbach, M. Kristiansen, H. Krompholz, "An Electron-beam Controlled Diffuse Discharge Switch", Proc. XVII International Conference on Phenomena in Ionized Gases, Budapest, Hungary, 1985, p. 626
Abstract:  Not Available
+ Analysis of Electrode Surface Damage in High Energy Spark Gaps
  A.L. Donaldson, M. Kristiansen, H. Krompholz, M. Hagler, L. Hatfield, G. Leiker, P. Predecki, G. Jackson, "Analysis of Electrode Surface Damage in High Energy Spark Gaps", Proc. 5th IEEE Pulsed Power Conf., Arlington, VA, USA, 1985, p. 457
Abstract:  Not Available
+ Arc Current, Voltage, and Resistance in a High Energy, Gas Filled Spark Gap
  B. Maas, H. Krompholz, M. Kristiansen, M. Hagler, "Arc Current, Voltage, and Resistance in a High Energy, Gas Filled Spark Gap", Proc. 5th IEEE Pulsed Power Conference, Arlington, VA, USA, 1985, p. 99
Abstract:  Not Available
+ Breakdown Development of Pulsed N2 and SF6 Gaps
  M. Giesselmann, I. Kusuma, W. Pfeiffer, and J. Wolf, "Breakdown Development of Pulsed N2 and SF6 Gaps", 5th IEEE Pulsed Power Conference, Arlington, Virginia, Conference Record, p. 84-87, June 10-12, 1985.
Abstract:  Not Available
+ Diagnostics of Pulsed Discharges
  M. Giesselmann, "Diagnostics of Pulsed Discharges", 1985 meeting of Short Time Physics, Bayreuth, Germany.
Abstract:  Not Available
+ Electromagnetic Mass Drivers
  "Electromagnetic Mass Drivers," Scientific Bull., Office of Naval Research Far East, Dept. of the Air Force Office of Scientific Research Far East, Jan.-Mar., vol. 10, no. 1, 1985 (with F. Rose).
Abstract:  Not Available
+ Experiment to Investigate Current Drive by Fast Alfven Waves in a Small Tokamak
  "Experiment to Investigate Current Drive by Fast Alfven Waves in a Small Tokamak," Proc. 6th AIP Topical Conf. Radio Freq. Plasma Heating, No. 129, Callaway Gardens, GA, 1985 (with J. Gahl, O. Ishihara, K. Wong and M. Hagler).
Abstract:  Not Available
+ High Current Surface Discharge Switch
  P.M. Ranon, H. Krompholz, M. Kristiansen, L.L. Hatfield, "High Current Surface Discharge Switch", Proc. 5th IEEE Pulsed Power Conf., Arlington, VA, USA, 1985, p. 276
Abstract:  Not Available
+ Increased Flashover Potential of Polymers
  "Increased Flashover Potential of Polymers," Proc. 5th IEEE Pulsed Power Conf., Arlington, VA, June 1985 (with L.L. Hatfield and G. Leiker).
Abstract:  Not Available
+ Inertial Confinement Fusion Research in Japan
  "Inertial Confinement Fusion Research in Japan," Scientific Bulletin, Dept. of the Navy Office of Naval Research Far East and Dept. of the Air Force Office of Scientific Research Far East 10(2), 171, 1985 (with M. Frank Rose).
Abstract:  Not Available
+ Pulsed Power Research in Japan
  "Pulsed Power Research in Japan," Scientific Bulletin, Dept. of the Navy Office of Naval Research Far East and Dept. of the Air Force Office of Scien­tific Research Far East 10(2), 169, 1985 (with M. Frank Rose).
Abstract:  Not Available
+ Striations in High Pressure Diffuse Discharges
  "Striations in High Pressure Diffuse Discharges," Proc. NATO Advanced Study Institute on Radioactive Processes in Discharge Plasma, Pitlochry, Scotland, June 23-25, 1985 (with K.H. Schoenbach, G. Schaefer, E. Strickland, and O. Ishihara).
Abstract:  Not Available
+ t in SF6 and SF6 - N2 Mixtures under Impulse Voltage Stress
  M. Giesselmann, I. Kusuma, W. Pfeiffer, and J. Wolf, "Discharge Development in SF6 and SF6 - N2 Mixtures under Impulse Voltage Stress", Proceedings of the Eighth International Conference on Gas Discharges and their Applications (GD'85) Oxford, U.K., p. 278-281, September 1985.
Abstract:  Not Available
+ Transmission Line Current Sensor
  H. Krompholz, K. Schoenbach, G. Schaefer, "Transmission Line Current Sensor", IEEE Instrumentation and Measurement Technology Conference, Tampa, Florida, USA 1985, p. 224
Abstract:  Not Available
Publication Year:  1984
+ An E-Beam Controlled Diffuse Discharge Switch
  K. Schoenbach, G. Schaefer, M. Kristiansen, H. Krompholz, H. Harjes, D. Skaggs, "An E-Beam Controlled Diffuse Discharge Switch", 16th IEEE Power Modulator Symposium, Arlington, Virginia, USA 1984, p. 152
Abstract:  Not Available
+ Antenna System Without Matching Circuitry for Unidirectional Propagation of Alfven Waves
  "Antenna System Without Matching Circuitry for Unidirectional Propagation of Alfven Waves," Proc. 3rd All Union Conf. Engrg. Problems of Fusion Reactors, Leningrad, USSR, June 20-22, 1984 (with H. Akiyama, J. Gahl, K. Rathbun and M.O. Hagler).
Abstract:  Not Available
+ Flashover Mechanism and Dielectric Strength of Gas / Solid Inter¬faces
  M. Giesselmann, W. Pfeiffer, "Flashover Mechanism and Dielectric Strength of Gas / Solid Inter¬faces", 1984 IEEE International Symposium on Electrical Insulation, Montreal, Canada, June 1984, Conference Record, p. 218-221
Abstract:  Not Available
+ Investigations of E-Beam Controlled Diffuse Discharge
  K. Schoenbach, G. Schaefer, M. Kristiansen, H. Krompholz, H. Harjes, D. Skaggs, "Investigations of E-Beam Controlled Diffuse Discharges", 4th Int. Symp. on Gaseous Dielectrics, Knoxville, TN, USA, 1984
Abstract:  Not Available
+ Recovery Measurements in a Spark Gap
  C. Yeh, H. Krompholz, M. Hagler, M. Kristiansen, "Recovery Measurements in a Spark Gap", 16th IEEE Power Modulator Symposium, Arlington, Virginia, USA 1984, p. 64
Abstract:  Not Available
Publication Year:  1983
+ A Multi-Spark Preionization Source for Diffuse Discharges Containing Attachers
  "A Multi-Spark Preionization Source for Diffuse Discharges Containing Attachers", Proc. 4th IEEE Pulsed Power Conf., Albuquerque, NM, June 1983 (with R. Cooper, G. Hutcheson, G. Schaefer, K.H. Schoenbach, and A.H. Guenther).
Abstract:  Not Available
+ An Introduction to Gas Filled Spark Gaps
  "An Introduction to Gas Filled Spark Gaps," Proc. ARO Workshop on Repetitive Spark Gap Operation, Tamarron, CO, Jan. 1983. DTIC No. AD-A132688.
Abstract:  Not Available
+ E-Beam Triode for Multiple Submicrosecond Pulse Operation
  "E-Beam Triode for Multiple Submicrosecond Pulse Operation," Proc. 4th IEEE Pulsed Power Conf., Albuquerque, NM, June 1983 (with H. Harjes, K. Schoen­bach, G. Schaefer and H. Krompholz).
Abstract:  Not Available
+ E-Beam Triode for Multiple Submicrosecond Pulse Operation
  H. Harjes, K. Schoenbach, G. Schaefer, H. Krompholz, M. Kristiansen, G. Leiker, L. Hatfield, "E-Beam Triode for Multiple Submicrosecond Pulse Operation", 4th IEEE Pulsed Power Conference, Albuquerque, New Mexico, USA, 1983, p. 474
Abstract:  Not Available
+ Electrode Erosion in a High Energy Spark Gap
  "Electrode Erosion in a High Energy Spark Gap," Proc. 4th IEEE Pulsed Power Conf., Albuquerque, NM, June 1983 (with A.L. Donaldson, M. Hagler, G. Jack­son, L. Hatfield and J. Marx).
Abstract:  Not Available
+ Nanosecond Current Probe for High Voltage Experiments
  H. Harjes, J. Doggett, J. Gahl, K. Zinsmeyer, H. Krompholz, K. Schoenbach, G. Schaefer, M. Kristiansen, "Nanosecond Current Probe for High Voltage Experiments", 4th IEEE Pulsed Power Conference, Albuquerque, New Mexico, USA 1983, p. 396
Abstract:  Not Available
+ Nanosecond Current Probe for High Voltage Experiments
  "Nanosecond Current Probe for High Voltage Experiments," Proc. 4th IEEE Pulsed Power Conf., Albuquerque, NM, June 1983 (with H. Harjes, J. Doggett, J. Gahl, K. Zinsmeyer, H. Krompholz, K. Schoenbach and G. Schaefer).
Abstract:  Not Available
+ Pulsed Flashover of Solid Dielectrics in Gases
  "Pulsed Flashover of Solid Dielectrics in Gases," Proc. 4th IEEE Pulsed Power Conf., Albuquerque, NM, June 1983 (with G. Jackson, L. Hatfield, G. Leiker and J. Marx).
Abstract:  Not Available
+ Pulsed Power Education
  "Pulsed Power Education," Proc. 4th IEEE Pulsed Power Conf., Albuquerque, NM, June 1983 (with A. Guenther, J. Ungvarsky, T. Skvarenina, A. Hyder, and H. Pugh).
Abstract:  Not Available
+ Pulsed Power Technology and Diffuse Discharges
  "Pulsed Power Technology and Diffuse Discharges," Proc. US-FRG Joint Seminar on Externally Contr. Diffuse Discharges," Bad Honnef, FRG, Aug. 1983 (with M.F. Rose).
Abstract:  Not Available
+ Repetitive Spark Gap Operation--A Review of the Tamarron Workshop
  "Repetitive Spark Gap Operation--A Review of the Tamarron Workshop," Proc. 4th IEEE Pulsed Power Conf., Albuquerque, NM, June 1983 (with M.O. Hagler).
Abstract:  Not Available
+ Solid State Pulsed Power Switching--A Review of the Tamarron Workshop
  "Solid State Pulsed Power Switching--A Review of the Tamarron Workshop," Proc. 4th IEEE Pulsed Power Conf., Albuquerque, NM, June 1983 (with W.M. Portnoy).
Abstract:  Not Available
+ Summary of the Capabilities of Repetitive Spark Gap Switches
  "Summary of the Capabilities of Repetitive Spark Gap Switches," Proc. ARO Workshop on Repetitive Spark Gap Operation, Tamarron, CO, Jan. 1983 (with I. Smith, T. Burkes, A. Guenther and G. Lauer). DTIC No. AD-A132688.
Abstract:  Not Available
+ Surface Charging of Insulators in Surface Discharge Switches
  "Surface Charging of Insulators in Surface Discharge Switches," Proc. Conf. Electrical Insulation and Dielectric Phenomena, Buckhill Falls, PA, Oct. 1983 (with R. Curry, L. Hatfield, V. Agarwal and G. Jackson).
Abstract:  Not Available
+ Surface Studies of Dielectric Materials used in Spark Gaps
  "Surface Studies of Dielectric Materials used in Spark Gaps," Proc. 4th IEEE Pulsed Power Conf., Albuquerque, NM, June 1983 (with G. Jackson, L. Hatfield, M. Hagler, J. Marx, A. Donaldson, G. Leiker, R. Curry, R. Ness, L. Gordon and D. Johnson).
Abstract:  Not Available
+ Surface Studies of Electrodes used in Spark Gaps
  "Surface Studies of Electrodes used in Spark Gaps," Proc. 4th IEEE Pulsed Power Conf., Albuquerque, NM, June 1983 (with G. Jackson, G. Leiker, L. Hatfield, M. Hagler, A. Donaldson, R. Ness and J. Marx).
Abstract:  Not Available
+ Triggering of Surface Discharge Switches
  "Triggering of Surface Discharge Switches," Proc. 4th IEEE Pulsed Power Conf., Albuquerque, NM, June 1983 (with R. Curry, D. Johnson, L. Hatfield, and A.H. Guenther).
Abstract:  Not Available
+ Voltage Recovery Measurements in a High Energy Spark Gap
  "Voltage Recovery Measurements in a High Energy Spark Gap," Proc. 4th IEEE Pulsed Power Conf., Albuquerque, NM, June 1983 (with C. Yeh and M. Hagler).
Abstract:  Not Available
Publication Year:  1982
+ Electrode Erosion in High Power Spark Gaps
  "Electrode Erosion in High Power Spark Gaps," Proc. 15th Power Modulator Symp., Baltimore, MD, June 1982 (with A. Donaldson, R. Ness and M.O. Hagler).
Abstract:  Not Available
+ Multichannel Surface Discharge Switch
  "Multichannel Surface Discharge Switch," Proc. Conf. Elec. Insulation and Dielectric Phenomena, Amherst, MA, Oct. 1982 (with D. Johnson and L.L. Hatfield).
Abstract:  Not Available
+ Optical Control of Diffuse Discharge Opening Switches
  "Optical Control of Diffuse Discharge Opening Switches," Proc. U.S. Army Workshop on Diffuse Discharge Opening Switches," Tamarron, CO, Jan. 1982 (with K.H. Schoenbach, G. Schaefer, L.L. Hatfield and A.H. Guenther) DTIC No. AD-A115883.
Abstract:  Not Available
+ Optical Control of Discharge Opening Switches
  "Optical Control of Discharge Opening Switches," Proc. US Army Workshop on Diffuse Opening Switches, Tamarron, CO, Apr. 1982 (with K.H. Schoenbach, G. Schaefer, A.H. Guenther and L.L. Hatfield). DTIC No. AD-A115883.
Abstract:  Not Available
+ Pre-Discharge Development at Interfaces between Gaseous and Solid Dielectrics
  W. Pfeiffer, M. Giesselmann, P. Völker, "Pre-Discharge Development at Interfaces between Gaseous and Solid Dielectrics", 1982 IEEE International Symposium on Electrical Insulation, Philadelphia, June 1982
Abstract:  Not Available
+ Pulse Flashover of Solid Dielectrics in Vacuum
  "Pulse Flashover of Solid Dielectrics in Vacuum," Proc. 10th Int. Symp. Discharges and Elec. Insulation in Vacuum, Columbia, SC, Oct. 1982 (with D. Johnson, L.L. Hatfield, J. Marx and A. Bowling).
Abstract:  Not Available
+ Spatial and Temporal Pre-Discharge Development at Insu¬lator Surfaces in Compressed Gases
  W. Pfeiffer, M. Giesselmann, and P. Völker, "Spatial and Temporal Pre-Discharge Development at Insu¬lator Surfaces in Compressed Gases", Proceedings of the Seventh International Confer¬ence on Gas Discharges and their Applications (GD'82) London, U.K., p. 277-279, September 1982
Abstract:  Not Available
Publication Year:  1981
+ Diffuse Discharge Opening Switches
  "Diffuse Discharge Opening Switches," Proc. NATO Advanced Study Institute on Breakdown and Discharges in Gases, Les Arcs, France, 1981 (with K.H. Schoen­bach, G. Schaefer, L.L. Hatfield and A.H. Guenther). NATO ASI Series B: Physics 89B, Plenum Press (1983), p. 415.
Abstract:  Not Available
+ Exploratory Concepts of Opening Switches
  "Exploratory Concepts of Opening Switches", Proc. US Army Workshop on Repetitive Opening Switches, 65-105, Tamarron, CO, Jan. 1981 (with K.H. Schoen­bach, A.H. Guenther and E.E. Kunhardt).
Abstract:  Not Available
+ Investigations of a 60 KV, 5 cm Spark Gap for Several Electrode, Insulator and Gas Types
  "Investigations of a 60 KV, 5 cm Spark Gap for Several Electrode, Insulator and Gas Types," Proc. 3rd IEEE Int. Pulsed Power Conf., Albuquerque, NM, June 1981 (with L.B. Gordon, M.O. Hagler and H.C. Kirbie).
Abstract:  Not Available
+ Magnetic Probe Measurements of Toroidal Eigenmodes in the Texas Tech Tokamak
  "Magnetic Probe Measurements of Toroidal Eigenmodes in the Texas Tech Tokamak," Proc. 4th Topical Conf. RF Plasma Heating, Austin, TX, Feb. 1981 (with P.D. Coleman, B.D. Blackwell and M.O. Hagler).
Abstract:  Not Available
+ Modular Instructional Material in Pulsed Power Technology
  "Modular Instructional Material in Pulsed Power Technology," Proc. 3rd IEEE Int. Pulsed Power Conf., Albuquerque, NM, June 1981 (with A.H. Guenther, J. Ungvarsky, F. Brockhurst, R.D. Franklin, A.K. Hyder and R.L. Gullickson).
Abstract:  Not Available
+ Opening Switches
  "Opening Switches," Proc. 3rd IEEE Int. Pulsed Power Conf., Albuquerque, NM, June 1981 (with K.H. Schoenbach, G. Schaefer, E.E. Kunhardt and A.H. Guenther).
Abstract:  Not Available
+ Plasma Applications
  "Plasma Applications," Proc. NATO Advanced Study Institute: Electrical Breakdown and Discharge in Gases, Les Arcs, France, July 1981 (with A.H. Guenther). NATO ASI Series B: Physics 89B, Plenum Press (1983), p. 383.
Abstract:  Not Available
+ Probe Measurements of the Magnetic Field Structure of Toroidal Eigenmodes in the Texas Tech Tokamak
  "Probe Measurements of the Magnetic Field Structure of Toroidal Eigenmodes in the Texas Tech Tokamak," Proc. 2nd All-Union Conf. Engrg. Problems of Thermo­nuclear Reactors 2, 54, Leningrad, USSR, June 23-25, 1981 (with P.D. Coleman, B.D. Blackwell and M.O. Hagler).
Abstract:  Not Available
+ Pulsed Power Education at Texas Tech University
  "Pulsed Power Education at Texas Tech University," Proc. 3rd IEEE Int. Pulsed Power Conf., Albuquerque, NM, June 1981 (with E.E. Kunhardt).
Abstract:  Not Available
+ Space Charge Effects in a Laser-Fiber Optics Triggered Multichannel Spark Gap
  "Space Charge Effects in a Laser-Fiber Optics Triggered Multichannel Spark Gap," Proc. 3rd IEEE Int. Pulsed Power Conf., Albuquerque, NM, June 1981 (with H.C. Harjes, E.E. Kunhardt, and L.L. Hatfield).
Abstract:  Not Available
+ Surface Damage of Dielectrics in a Spark Gap
  "Surface Damage of Dielectrics in a Spark Gap," Proc. 3rd IEEE Int. Pulsed Power Conf., Albuquerque, NM, June 1981 (with G.L. Jackson, K.-C Yuan and L.L. Hatfield).
Abstract:  Not Available
Publication Year:  1980
+ Discharge Phenomena in Pulsed Power Applications
  "Discharge Phenomena in Pulsed Power Applications", Proc. NSF Workshop on Plasma Chemistry and Arc Technology, Univ. of Minnesota, Minneapolis-St. Paul, MN, 1980 (with A.H. Guenther and A. Garscadden).
Abstract:  Not Available
+ Investigations of Reed Switch Dynamics When Switching Heavy Loads
  "Investigations of Reed Switch Dynamics When Switching Heavy Loads," Proc. 10th Int. Conf. Contact Phenomena, Bucharest, Hungary, Aug. 25-29, 1980 (with B. Miedzinski).
Abstract:  Not Available
+ Probe Measurements of the Magnetic Field Structure of Fast Wave Toroidal Eigenmodes
  "Probe Measurements of the Magnetic Field Structure of Fast Wave Toroidal Eigenmodes," Proc. Int. Symp. Heating in Toroidal Plasmas, Como, Italy, 1980 (with P.D. Coleman, B.D. Blackwell and M.O. Hagler).
Abstract:  Not Available
Publication Year:  1979
+ An Electron-Beam-Triggered Spark Gap
  "An Electron-Beam-Triggered Spark Gap," Proc. 2nd IEEE Int. Pulsed Power Conf., Lubbock, TX, June 12-14, 1979 (with L.L. Hatfield, H.C. Harjes, A.H. Guenther and K.H. Schoenbach).
Abstract:  Not Available
+ Applications of Electron Beams for Precise Switching of High Voltages
  "Applications of Electron Beams for Precise Switching of High Voltages," Proc. 3rd Int. Topical Conf. High Power Electron and Ion Beam Res. and Techn., Novosibirsk, USSR, July 3-6, 1979 (with M. Newton, K. McDonald, E.E. Kunhardt and A.H. Guenther).
Abstract:  Not Available
+ High Power Switch Capabilities
  "High Power Switch Capabilities," Proc. Switching and Pulse Compression Conf., Venice, Italy, 1979 (with H. Odem, T. Burkes, W. Portnoy, M. Hagler and J.P. Craig).
Abstract:  Not Available
+ Investigations of Fast Insulator Surface Flashover
  "Investigations of Fast Insulator Surface Flashover," Proc. 2nd IEEE Int. Pulsed Power Conf., Lubbock, TX, June 12-14, 1979 (with J.E. Thompson, J. Lin and K. Mikkelson).
Abstract:  Not Available
+ Investigations of Various Probe Sheath Materials in the Texas Tech Tokamak
  "Investigations of Various Probe Sheath Materials in the Texas Tech Tokamak," Proc. 8th Symp. Engrg. Problems of Fusion Res., San Francisco, CA, Nov. 1979 (with P.D. Coleman, B.D. Blackwell, S.R, Beckerich, C.K. Rothstein and M.O. Hagler).
Abstract:  Not Available
+ Simulation of Inductive and Electromagnetic Effects Associated with Single and Multichannel Triggered Spark Gaps
  "Simulation of Inductive and Electromagnetic Effects Associated with Single and Multichannel Triggered Spark Gaps," Proc. 2nd IEEE Int. Pulsed Power Conf., Lubbock, TX, June 12-14, 1979 (with S. Levinson, E.E. Kunhardt and A.H. Guenther).
Abstract:  Not Available
Publication Year:  1978
+ Description of the Texas Tech Tokamak
  "Description of the Texas Tech Tokamak," Proc. Small Toroidal Plasma Devices Users Mtg., 7, May 18, 1978, Rept. DOE-ET-78-G--05-5918 (with S.O. Knox, H.C. Kirbie, R.C. Cross and M.O. Hagler).
Abstract:  Not Available
+ High Power Switching Capabilities
  "High Power Switching Capabilities," 13th Pulsed Power Modulator Symp., SUNY/Buffalo, NY, June 20-22, 1978 (with T.R. Burkes, J.P. Craig, M.O. Hagler and W.M. Portnoy).
Abstract:  Not Available
Publication Year:  1977
+ An Experimental Arrangement for Laser Beat Heating of Plasma
  "An Experimental Arrangement for Laser Beat Heating of Plasma," Proc. 7th Symp. on Engrg. Problems of Fusion Research, 1615, Oct. 25-28, 1977 (with E.Y. Chu, R. Druce, L. Gordon, J. Jasper and M.O. Hagler).
Abstract:  Not Available
Publication Year:  1976
+ Laser Heating of Magnetized Plasma
  "Laser Heating of Magnetized Plasma," Proc. 1st Minicourse on Fusion, Austin, TX, May 26-28, 1976 (with M.O. Hagler).
Abstract:  Not Available
+ Switching Requirements for Fusion Reactors
  "Switching Requirements for Fusion Reactors," Proc. DoD Workshop on Pulsed Power, NSWC, White Oakes, Sept. 20-23, 1976.
Abstract:  Not Available
Publication Year:  1975
+ A Helical Antenna for Exciting Azimuthally Asymmetric Alfven Waves
  "A Helical Antenna for Exciting Azimuthally Asymmetric Alfven Waves", Proc. US-Australian Workshop on Plasma Waves, Australia, Feb. 13-18, 1975 (with S.O. Knox, F.J. Paoloni and M.O. Hagler).
Abstract:  Not Available
Publication Year:  1974
+ Carbon Dioxide Laser Interaction with Magnetized Plasma
  "Carbon Dioxide Laser Interaction with Magnetized Plasma," IEEE '74 Region VI Conf. Proc., Albuquerque, NM, 1974 (with G.M. Molen).
Abstract:  Not Available
+ Damping of the Fast Wave and Plasma Heating by an Unidentified Mechanism
  "Damping of the Fast Wave and Plasma Heating by an Unidentified Mechanism," Proc. 2nd Topical RF Plasma Heating, Texas Tech Univ., Lubbock, TX, June 20­22, 1974, D8 (with R. Dollinger, J. Bergstrom, M.O. Hagler and F.J. Paoloni).
Abstract:  Not Available
+ Experimental Investigations of a Helical Antenna for Exciting Alfven Waves
  "Experimental Investigations of a Helical Antenna for Exciting Alfven Waves," Proc. 2nd Topical Conf. RF Plasma Heating, Texas Tech Univ., Lubbock, TX, June 20-24, 1974, C2 (with S.O. Knox, F.J. Paoloni and M.O. Hagler).
Abstract:  Not Available
+ Simple, Solid Dielectric Start Switch
  "Simple, Solid Dielectric Start Switch," Proc. Int. Conf. Energy Storage, Compression and Switching, Torino, Italy, Nov. 5-7, 1974 (with W.C. Nunnally and M.O. Hagler). Published by Plenum Publishing Corp.
Abstract:  Not Available
Publication Year:  1973
+ Plasma Heating and Damping of the Fast Wave Near the Second Harmonic of the Ion Cyclotron Frequency
  "Plasma Heating and Damping of the Fast Wave Near the Second Harmonic of the Ion Cyclotron Frequency," Proc. 6th Eur. Conf. Contr. Fusion and Plasma Phys., Moscow, USSR, July 30 - Aug. 3, 1973 (with R. Dollinger, M.O. Hagler and J. Bergstrom).
Abstract:  Not Available
Publication Year:  1972
+ Enhanced Energy Transfer to a Cylindrical Plasma by an Alfven Wave
  "Enhanced Energy Transfer to a Cylindrical Plasma by an Alfven Wave," Proc. 1st Topical Conf. RF Plasma Heating, Texas Tech Univ., Lubbock, TX, July 6-8, 1972, A6 (with D.B. Lancaster and M.O. Hagler).
Abstract:  Not Available
+ Fast Plasma Heating for Thermonuclear Power (AFOSR-69-1757)
  "Fast Plasma Heating for Thermonuclear Power (AFOSR-69-1757)," Proc. AFOSR Contractors Meeting, Univ. Rochester, Rochester, NY, June 7-9, 1972 (with M.O. Hagler).
Abstract:  Not Available
+ Fast Wave Damping at the Second Harmonic of the Ion Cyclotron Frequency
  "Fast Wave Damping at the Second Harmonic of the Ion Cyclotron Frequency," Proc. 5th Eur. Conf. Contr. Fusion and Plasma Phys., Grenoble, France, Aug. 21-25, 1972, 117 (with J.E. Cato, C.N. Watson-Munro and M.O. Hagler).
Abstract:  Not Available
+ Fast Wave Propagation and Damping at the Second Harmonic of the Ion Cyclotron Frequency
  "Fast Wave Propagation and Damping at the Second Harmonic of the Ion Cyclotron Frequency," Proc. 1st Topical Conf. RF Plasma Heating, Texas Tech Univ., Lubbock, TX, July 6-8, 1972, B4 (with J.E. Cato, C.N. Watson-Munro and M.O. Hagler).
Abstract:  Not Available
Publication Year:  1971
+ Axial Magnetic Field Effects in a CO2 Laser Discharge
  "Axial Magnetic Field Effects in a CO2 Laser Discharge," Proc. 10th Int. Conf. Phenomena in Ionized Gases, Oxford, England, Sept. 14-17, 1971, p. 15 (with M.O. Hagler, G.M. Molen and L.G. Roseland).
Abstract:  Not Available
+ Current Practices and Trends in European Engineering Education
  "Current Practices and Trends in European Engineering Education," SWIEEECO Conf. Rec., Apr. 1971 (with M.O. Hagler).
Abstract:  Not Available
Publication Year:  1970
+ A Review of Fusion Reactor Design
  "A Review of Fusion Reactor Design," Proc. Frontiers Power Techn. Conf., Oklahoma State Univ., Stillwater, OK, Oct. 15-16, 1970 (with M.O. Hagler).
Abstract:  Not Available
+ Undergraduate Laser Experiments
  "Undergraduate Laser Experiments," SWIEEECO Conf. Rec. 53 (1970) (with G.M. Molen, C.R. Parten and M.O. Hagler).
Abstract:  Not Available
Publication Year:  1969
+ Investigations of the Macaluso-Corbino Effect in a 3.39 Micron He-Ne Laser
  "Investigations of the Macaluso-Corbino Effect in a 3.39 Micron He-Ne Laser," Proc. 9th Int. Ionization Conf., Bucharest, Rumania, 1969 (with M.O. Hagler and V.C. West).
Abstract:  Not Available
+ Laser Experiments for Undergraduate Electrical Engineering Students
  "Laser Experiments for Undergraduate Electrical Engineering Students," SWIEEECO Conf. Rec., Apr. 1969 (with L.N. Peckham and M.O. Hagler).
Abstract:  Not Available
+ Polarization Modulation Using the Macaluso-Corbino Effect
  "Polarization Modulation Using the Macaluso-Corbino Effect," SWIEEECO Conf. Rec. 7D1, Apr. 1969 (with V.C. West and M.O. Hagler).
Abstract:  Not Available
Publication Year:  1968
+ Controlled Thermonuclear Fusion--Some Recent Developments
  "Controlled Thermonuclear Fusion--Some Recent Developments," IEEE Reg. III Conf. Rec., Apr. 1968 (with M.O. Hagler).
Abstract:  Not Available
+ Current Investigations of High Power RF Heating of Magneto-plasma
  "Current Investigations of High Power RF Heating of Magneto-plasma," IEEE Reg. III Conf. Rec., Apr. 1968 (with J.E. Cato).
Abstract:  Not Available
+ Investigations of RF Energy Couplers for Resonant Plasma Heating
  "Investigations of RF Energy Couplers for Resonant Plasma Heating," SWIEEECO Conf. Rec., Apr. 1968 (with J.Hipp).
Abstract:  Not Available
+ Plasma Heating and Wave Propagation at Harmonics of the Ion Cyclotron Frequency
  "Plasma Heating and Wave Propagation at Harmonics of the Ion Cyclotron Frequency," Proc. European Conf. Controlled Fusion and Plasma Physics, Stock­holm, Aug. 1967; also Plasma Phys. 10, 460 (1968) (with A.A. Dougal).
Abstract:  Not Available
+ The Feasibility of Emergency Power Transmission with CO2 Lasers
  "The Feasibility of Emergency Power Transmission with CO2 Lasers," Proc. Frontiers of Power Techn. Conf., Stillwater, OK, Oct. 1968 (with M.O. Hagler).
Abstract:  Not Available
Publication Year:  1967
+ Plasma Heating and Wave Propagation at Harmonics of the Ion Cyclotron Frequency
  "Plasma Heating and Wave Propagation at Harmonics of the Ion Cyclotron Frequency," Proc. European Conf. Controlled Fusion and Plasma Physics, Stock­holm, Aug. 1967; also Plasma Phys. 10, 460 (1968) (with A.A. Dougal).
Abstract:  Not Available