High power microwave breakdown in slots

Summary form only given. FOA has together with Chalmers University started a research effort to theoretically and experimentally investigate the physics of high power microwave (HPM) breakdown in slots, with the goal to gain understanding of microwave breakdown tail erosion effects in slots and associated microwave carrier frequency conversion. Microwave breakdown phenomena have previously been studied at FOA and Chalmers. In this paper, experimental results of HPM breakdown in slots are presented, for plane wave HPM illumination towards metallic plane sheets with slots of various geometries. The HPM source used was a 37 GHz BWO capable of generating 15 MW in 4 ns pulses. The incident microwave electric field strengths have been measured using a hot electron detector, which also was used to measure the tail erosion effect of the pulse partially absorbed by the microwave breakdown in the slot. It was found that the threshold for the incident field to cause breakdown is higher the wider the slot, as expected due to the field enhancement effect. Statistical effects on the microwave breakdown in the slots have also been observed, in the sense that the breakdown happens only for a few of the incident pulses.