Microwave Gas Breakdown in Tunable Evanescent-Mode Cavity Resonators

Microwave gas breakdown in strongly-coupled evanescent-mode cavity resonators in atmospheric pressure and room temperature is investigated both numerically and experimentally. This high- Q resonator is widely tunable by changing the gap between its loading post and top wall. In this letter, we study the effect of different gap spacings on breakdown characteristics of this resonator. Good agreement is observed between measured breakdown powers and ones by plasma simulations for resonators with gaps of 14.8-51.2 μm, working in the 6-8.25 GHz frequency range with input breakdown power in the range of 45-48 dBm.