Short Pulse High Power Microwave Surface Flashover

Summary form only given. High power microwave (HPM) surface flashover is investigated in order to gain a better understanding of this phenomenon and reduce the limitations it imposes on transmitted power levels. The experimental setup is designed to produce window flashover without the influence of a triple point. The HPM source for this testing is an experimental virtual cathode oscillator (vircator) capable of producing greater than 50 MW for 100 ns with an adjustable frequency from 3 to 5 GHz. This work builds on previous testing using a magnetron producing 5 MW for 4 mus at 2.85 GHz. The dominant modes of the vircator and magnetron are the circular TE₁₁ and rectangular TE₁₀ modes respectively, with the electric field component in both setups normal to the direction of propagation, yielding comparable conditions. Due to the large differences in output power and pulse length, the two setups operate in different regimes and mechanisms take on differing degrees of importance. Additional factors under investigation include gas pressure, composition, temperature, and air speed. Diagnostic equipment permits the analysis of power levels with sub-nanosecond resolution. Experimental results are compared with data from literature, previous testing, and Monte Carlo simulations.