Effects of trace oxygen on the self-oscillation of positive glow corona in nitrogen near atmospheric pressure

Abstract

Abstract Positive glow corona is a stable and quasi-homogenous form of corona discharge with periodic current pulses, which appear in atmospheric plasma applications, high voltage apparatus, and grounded structures during thunderstorms. The debate on the seed electron source responsible for the pulsing nature of the positive glow corona has persisted for decades. This paper presents a numerical simulation study of a 1D coaxial positive glow corona in pure N2 with trace oxygen content ranging from 1% to 1 ppm. The reduction of oxygen content has been found to cause weaker glow current magnitude, longer time-to-crest, shorter oscillation periods, and more positive ion sheaths. As the trace oxygen decreases from 1% to 10 ppm, the dominant source of secondary electrons transits from both detachment and photoionization to photoionization only. As the trace O2 content drops from 0.1%, the dominant photoionization within the ionization layer transits from the photoionization of O2 molecules to the direct photoionization of N2 molecules. For high purity nitrogen, the detachment of O− dominates and the detachment of O2 − can be neglected. As the trace oxygen decreases from 1% to 10 ppm, the dominant molecules involving O− detachment transit from N2 and O to N2(A). The dominant ionization responsible for electron multiplication during the electric field recovery shifts from the direct ionization of O2 and N2 in 1% trace oxygen to the associative ionization between N2(A) and N2(a′) and the direct ionization of N2 in 1 ppm trace oxygen.