Short pulse high power microwave surface flashover

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2008-12

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Abstract

High power microwave (HPM) systems are often limited in transmitted power density and pulse length by surface flashover occurring across dielectric interfaces. This phenomenon can absorb and/or reflect the incident microwave pulse, causing transmission to cease and potentially damaging the microwave source and the dielectric interface itself. The experimental setup is designed to produce and study HPM surface flashover without the influence of a field enhancing triple point. A reflex triode virtual cathode oscillator (vircator) is fed by an 8-stage Marx generator and pulse forming line to produce a 50 MW, 50 ns pulse with an adjustable frequency from 3 to 5 GHz. This work builds on previous research using a Magnetron generated 5 MW, 4 μs pulse at 2.85 GHz, which is comparable to the current setup, but due to differences in power and pulse length the mechanisms involved have differing impacts on the flashover process. Also under investigation is the influence of factors such as gas pressure and composition. Diagnostics are designed to study the transmitted and incident power levels with sub-nanosecond resolution. Experimental results are discussed and compared with previous testing, literature, and Monte Carlo simulation models.

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