First Negative Corona Pulses in 70% N₂+30%SF₆Mixture

Abstract

Waveforms of the first negative corona current pulses in a 70% N 2 +30% SF 6 mixture at pressures of 13.33, 26.66 and 40 kPa have been studied as a function of overvoltage ranging from 0 to 100%. Near the corona threshold, the pulses, taking the form of a simple hump, are governed by the secondary electron emission due to a positive-ion impact. At moderate overvoltage, the formation of a double-peaked pulse was observed. This phenomenon can be explained in terms of the effect of photoemission and secondary electron emission. At higher overvoltages, peculiar current waveforms were observed. This phenomenon was explained by the association of the development of a cathode-directed streamer and its interaction with a cathode surface.