The mechanism of electrical breakdown of gases, initiated by a large number of electrons

Abstract

The mechanism of breakdown in uniform fields was investigated in humid air, dry air, oxygen, hydrogen and nitrogen at atmospheric pressure, using a large number of initial electrons (similar 104) released from the cathode as a delta function at the start of a high-voltage rectangular pulse applied to the discharge gap. The threshold breakdown voltages were about 30% higher than the DC breakdown voltages reported by others. The formative times at threshold and at overvoltages indicated that up to a critical overvoltage, breakdown takes place by the multiple-avalanche Townsend mechanism, due to a photoelectric secondary effect at the cathode. The magnitudes of the critical overvoltages were not significantly less than those with a single initial electron obtained by other workers. For overvoltages higher than the critical, there was a transition region, at the end of which, breakdown transforms to the single-avalanche streamer mechanism.