Prebreakdown phenomena and formation processes of low pressure glow discharges in N2, O2, and N2/O2 mixtures

Abstract

The prebreakdown phenomena and the resulting transient processes from the prebreakdown phenomena to the glow discharge in low-pressure N2, O2 gases, and N2/O2 mixtures were investigated. When the applied voltage was a lower overvoltage ratio less than about 2%, nonprebreakdown phenomenon was observed, and the overvoltage ratio was independent of the gas materials. This phenomenon, however, was observed at the overvoltage ratio of higher than about 3%. The prebreakdown phenomenon in N2 gas differed from those in O2 gas, and formed pulseless components. On the other hand, those in O2 gas formed pulsed components. The prebreakdown phenomenon in N2 gas changed to a pulsed discharge by mixing it with a small amount of more than 0.3% O2 gas. These transient processes from the prebreakdown phenomena to the glow discharges were also observed by a high-speed video camera. As a result, the formation processes of the glow discharge became clear.

Characteristics of the N2/O2 mixtures

“…It is almost the same as that in our previous papers [1][2] except for the structure of the electrodes forming the gap. A pair of stainless steel electrodes consisted of a circular plate with a radius of 85 mm, and its edge and supports covered with Teflon pipes to prevent the generation of a discharge outside the gap.…”

“…THE prebreakdown phenomena and the transient processes from those phenomena to the glow discharge in low pressure Ar, N 2 and O 2 gases, and Ar/O 2 and N 2 /O 2 mixtures have already been investigated by the authors [1][2]. Some interesting finding on the oscillations observed during the transition processes from Townsend to glow discharges in low pressure gas discharges were also reported experimentally and theoretically by Phelps et al [3][4][5][6].…”

“…The photon and voltage waveforms at higher than an approximate to 3% overvoltage ratio in N 2 /O 2 mixtures (O 2 <0.3%) formed a non-pulsed (pulseless) component as shown in Figure 3b. Moreover, the light (photon) and voltage waveforms at the overvoltage ratio of Δ≥3% in the N 2 /O 2 mixtures (0.3%≤O 2 <0.8%) formed an pulses superimposed on the non-pulsed component as shown in Figure 3c, and these changed to the pulses at the overvoltage ratio of Δ≥3%, O 2 ≥0.8% as shown in Figure 3d [2,[7][8]. Furthermore, the waveform of the photon did not correspond to that of voltage as shown in Figure 3d, i.e.…”

“…The prebreakdown phenomena of the glow discharges observed under low-pressure were divided into four types [2] according to their characteristics as shown in Figure 3.…”

“…The light (photon), voltage and current waveforms of prebreakdown phenomena and the onset voltage of glow discharge were measured under conditions of 1≤ pd≤ 6 (Torr·cm) for N 2 /O 2 mixtures. From these results it became clear under the given conditions, the forms of prebreakdown phenomena of the glow discharges observed under lowpressure N 2 /O 2 mixtures were divided into four types [2], and these appearance characteristics were expressed schematically and discussed.…”