Transient Processes During Formation of a Steady-State Glow Discharge in Air

Abstract

This paper describes the investigation of an atmospheric-pressure glow discharge in air at a current of 0.05-0.3 A. Before the glow discharge is established, a preliminary nonsteady temporal stage is available in the gap. The principal process, which governs with the nonsteady-state discharge behavior, is the glow-to-spark transition phenomenon. The transition is initiated due to the explosive emission instability in the near-cathode layer of glow-type discharge that results in a microexplosion of the cathode surface and appearing of a spark cathode spot. At a low current, the spot is extinguished, so that the discharge starts burning again in one of the glow modes. After that, a new act of transition occurs and so on. The preliminary nonsteady-state stage ensures two prerequisites. First, an effective gas pressure decreases to a low value. Second, due to microexplosions, conditioning of the cathode surface is provided. Both factors facilitate establishing the normal glow discharge.Index Terms-Atmospheric-pressure plasma jets, glow-to-spark transition, high-pressure glow discharge.

Low-current discharge plasma jets in a gas flow. Application of plasma jets

“…1 [39]. In the photographs we see the negative glow region of the glow discharge resting, sort of, on the surface of the cathode, a 0.6-0.7-mm discharge column, and the Faraday dark space in between.…”

“…As seen from Fig. 2 [39], the effective pressure inside the discharge region is within the range of 120-200 Torr, which is much less than the initial pressure in the chamber, which allows the glow discharge to be sustained in the steady-state mode without cathode spot formation. However, occasional transitions to the spark discharge mode take place under these conditions as well.…”

“…However, in some specific conditions, a glow-discharge current was observed [28,33,34,38,39]. It concerns, first and foremost, discharges with a small volume of the plasma column, when its diameters of is only ~1 mm or smaller.…”

“…In view of the aforesaid, it will be useful to look at the results of research on glow discharges in air at atmospheric pressure with the discharge gap d = 1 mm, within the current range i = (0.05 -0.27) A [39]. It was demonstrated that prior to settling as a steady-state glow discharge, there is a certain time interval of spontaneous transitions from one form of discharge burning to another [39].…”

“…It was demonstrated that prior to settling as a steady-state glow discharge, there is a certain time interval of spontaneous transitions from one form of discharge burning to another [39]. Distinguishable are the following stages within that time interval: spark discharge; glow-type discharge without a cathode spot; glow discharge with a cathode spot; discharge with a cathode spot and diffuse channel attached to the cathode spot; formation and spontaneous extinguishing of cathode spots; and short-time current interruptions.…”