Optical Observation of Gas Discharge Induced by High-Power and Short-Pulsed Microwave

概要

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The temporal and spatial evolution of gas discharge induced by a high-power, short-pulsed microwave (HPM) was observed using a high-speed image converter camera. The HPM with the peak power of 20 MW, frequency of 13 GHz, and pulse duration of 14 ns was irradiated uniformly into a gap between two spherical electrodes biased to a DC voltage less than the gap breakdown voltage. The streak images show two different breakdown mechanisms depending on air pressure. In the high-pressure region above about 300 Torr, the microwave-induced discharge begins at several points on the gap axis. When these local discharges increase sufficiently to link together with each other, the gap breakdown occurs. The gap breakdown is delayed by 30–300 ns depending on gas pressures and applied DC voltages. In the low-pressure region less than 300 Torr, on the other hand, a two-stage breakdown occurs. In the first stage, a single large discharge luminescence appears in the gap center at the time of the microwave injection and is followed by another discharge between the first discharge and two electrodes. After approximately 0.1–20 microseconds of the first stage discharge, the second-stage discharge appears followed by the gap breakdown.
Publication Office, Japanese Journal of Applied Physics, Faculty of Science, University of Tokyoの論文
2001-02-28