REP-rate operation of a ∼200 KV sealed-tube reflex-triode vircator at ∼200 A/cm2

• Published in: 2014 IEEE 41st International Conference on Plasma Sciences (ICOPS) held with 2014 IEEE International Conference on High-Power Particle Beams (BEAMS) p. 1
• Main Authors: Parson, Jonathan M., Bragg, James-William B., Taylor, Mark, Barnett, David, Kelly, Patrick, Lynn, Curtis F., Holt, Shad, Dickens, James C., Neuber, Andreas A., Mankowski, John J.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.05.2014
• Subjects: Anodes; Cathodes; Electron tubes; Steel
• ISBN: 9781479927111; 1479927112
• ISSN: 0730-9244; 2576-7208
• DOI: 10.1109/PLASMA.2014.7012435

Summary form only given. Thermal limitations of anode and cathode materials have shown to negatively impact operation of cold-cathode high-power microwave (HPM) sources. High pulse-repetition-frequency (PRF) operation of these devices exacerbates the problems already experienced in single shot mode where cold-cathode devices, specifically carbon fiber cathodes, are plagued by plasma formation on the anode and cathode followed by plasma/gas expansion that causes impedance collapse of the anode-cathode (A-K) gap. Hence, for frequency stable, repetitive operation, cold-cathode HPM devices require the use of thermally robust electrode materials and ultra-clean surfaces, leading to repeatable tube operation. This study focuses on burst-mode operation of an HPM sealed tube reflex-triode virtual-cathode-oscillator (vircator) for PRFs greater than 100 Hz. The vircator is driven by a 54 J, ~200 kV Marx generator with an approximate pulse width of 50 ns FWHM, and the vircator chamber has an empty volume of approximately 5 L with background pressures in the low 10 -9 Torr. The anode materials studied include grade-1 titanium (TiG1), nickel 201L (Ni201L), and stainless steel 316L (SS316L); all in combination with a carbon fiber cathode. Empirically observed outgassing characteristics in conjunction with anode thermal modeling are presented under single-shot and rep-rate conditions. In addition, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) techniques were employed to investigate anode and cathode surface integrities before and after vircator operation.