Transition of an atmospheric-pressure glow discharge from the diffuse to spark phase

The dynamics of glow and the electrical characteristics of a nanosecond glow discharge in the course of a transition from the diffuse to spark phase have been studied in a rod-plane electrode geometry in air at atmospheric pressure. For this purpose, a sequence of alternating-polarity voltage pulses with an amplitude decaying from 135–170 kV was applied to the interelectrode gap with a length of 5–6 cm. It is established that the spark channel formation is preceded by the stage of diffuse glow and that the spark parameters are correlated with the statistical features of the stage of gap shortage (bridging) preceding the diffuse glow. This analysis also revealed the important role of thermal processes in the dynamics of glow discharge development.