Microwave tubes that do not require an externally applied magnetic field, such as vircators and MILOS have been the HPM sources of choice at TTU. The development of vircator HPM sources has been ongoing more that 20 years, with MILO source development having been added in the last few years. Recent efforts have concentrated on the technologies necessary to produce compact (typically six inches in diameter), sealed-tube devices. Current laboratory vircator sources are baked out and then sealed, utilizing only getter materials and active ion pumping during operation. Ongoing research is focused on high-performance anode and cathode materials that are compatible with the ultra-high vacuum pressures, and on optimizing the geometry and resonant behavior of the vircator cavity to maximize power output and efficiency. The compact MILO source, being a more recent development, has only been constructed as a conventional low-vacuum tube and is undergoing initial testing and improvement prior to development of a sealed-tube variant. Nonlinear transmission lines (NLTLs) are also being investigated for their demonstrated potential as agile mesoband HPM sources. Application of axial bias fields has been shown to stimulate damped gyromagnetic precession and generate powerful microwaves signals. Current efforts included isolating critical ferromagnetic material properties, developing a computational model of the device, and determining optimal device geometry. Development is also proceeding on a pulsed ring down antenna array with the goal of having sources mounted on multiple vehicles. Firing of the individual sources will be controlled using GPS timing and coordinated to place a “hot spot” on a desired location.
Dr. James Dickens, Associate Director, C. B. Thornton Professor