Dynamics of structure of pulsed discharge in nitrogen and argon at different pressures in a "pin to plane" gap

Abstract

Using high-speed shooting and shadow photography, the spatial structure of a pulsed discharge in a 1.5 mm long "pin(cathode)-plane" gap in nitrogen and argon in the pressure range from 0.25 to 2 atm was studied. It has been found that a spark discharge is realized in nitrogen and a diffuse form of discharge is realized in argon. For both cases, the presence of a microstructure of discharges in the studied pressure range was found, when the discharge is an aggregation of a large number of micron-diameter channels. It is shown that for each gas the dynamics of the discharge glow structure remains similar at different pressures. It has been established that the glow and microstructure of the discharge in nitrogen are similar to those in air. Keywords: spark discharge, diffuse discharge, microstructure, method of shadow photography, high-speed shooting.

Investigation of plasma properties in the phase of the radial expansion of a spark channel in the ‘pin-to-plate’ geometry

“…Figure 3 shows the discharge shadowgrams at different time moments relative to the moment of the electrical breakdown. It can be seen that the discharge develops in a microchannel form, similarly to [19][20][21]. Recording of microchannels begins at the moment of breakdown near the pin, and they close the discharge gap in 2 ns after the breakdown.…”

“…The experimental setup for the discharge study is shown in figure 1. The experimental equipment and the shadow photography technique are described in detail in [19]. In general terms the experiments consisted of the following.…”

“…After electrical breakdown of the gap an oscillatory process arises with exponential attenuation of the current and voltage amplitudes. The oscillation period is 1 μs, and the current amplitude and its decay time were 1.5 kA and 2 μs [19]. The time moment of the beginning of the current growth and voltage drop was taken as a time moment (t bd in figure 2) of the electrical breakdown.…”

“…Practically, the effect of contraction or filamentation of a discharge is very important, which possibly determines its transition to the spark stage [16][17][18]. For example, in a number of works [19][20][21][22][23] it was found that a visually solid-looking spark discharge channel in the pin-toplate geometry is a bundle of a large number of microchannels that exhibit complex dynamics. The microchannel structure of the discharge was recorded by shadow photography.…”

“…It should be noted that despite the large number of studies on the spark discharge using the method of shadow photography, only a few reveal a microchannel internal structure of the discharge [19][20][21][22][23].…”