Current-channel radiation dynamics of a pulsed-periodic atmospheric pressure discharge in flowing argon
摘要
The temporal characteristics of optical radiation from plasma in the current channel of a glow discharge at atmospheric pressure are presented. The study was made in a pulsed discharge with a current ranging from 40 to 100 mA, a discharge voltage of 250–300 V, pulse durations of 10–15 μs, and frequencies of 50–100 kHz. The discharge operated in a 6 mm interelectrode gap, utilizing an argon flow at a rate of 1000 sccm. At a threshold current of 40–60 mA, the initially uniform spatial distribution of plasma radiation intensity transformed into a regular structured pattern, characterized by brightly luminous regions separated by darker gaps, an appearance similar to bead lightning. Time-resolved imaging techniques revealed the following trends. A spatially-periodic glow structure emerged in the discharge column during the current decay stage and persisted throughout the time intervals between discharge current pulses at near-zero voltage. Conversely, when the current reached its peak value, this structure transformed into a uniform distribution. This article explores the influence of phenomena, particularly those associated with the development of gas-dynamic instability which arises at the interface between cold and heated gas flows as a result of convective cooling of the discharge gap, on the dynamics of plasma glow.