Formation of the microchannel structure of a spark discharge in air in the gap spike-plane

Abstract

The formation of the microchannel structure of a spark dischargein the gap spike (cathode)-plane of 1.5 mm length in the air of atmosphericpressure was studied by the method of shadow photography.The images with the concurrent descent of microchannel diameter sand thenumber of microchannel increase in the cathode region on the time intervalof 5 ns were recorded. The obtained data are explained in the frames ofthemicrostructure formation mechanism at the expense of the front instabilityof the ionization wave. The parameters characterizing the process of themicrostructure formation are estimated, and they agree with the experimentaldata. Keywords: spark discharge, ionization wave, ionization instability, microstructure, method of shadow photography.\

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

“…1. A part of its elements are characterized in detail in [19,21]. Pulsed voltage generator ensured negative polarity output pulse with an amplitude of 25 kV and a level 0.1−0.9 rise time of approximately 7 ns.…”

“…The vacuum chamber use, in contrast to previous experiments [19][20][21]24], required the optical scheme change. Additional lens O 1 was used, which was located at a double focal length from the discharge gap and made its image in a scale of 1 : 1.…”

“…Despite a long period of research, a number of gasdischarge phenomena remain poorly understood. They include the discharge microstructure [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25], when the current channel is a set of a large number of microchannels (filaments). The microstructure was detected during discharges in air at atmospheric pressure: initially by the autograph method on the surface of a flat electrode [11][12][13][14][15][16][17][18], then by shadow and interference methods of high spacetime resolution in the volume of the discharge gap [18][19][20][21][22][23][24][25].…”

“…They include the discharge microstructure [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25], when the current channel is a set of a large number of microchannels (filaments). The microstructure was detected during discharges in air at atmospheric pressure: initially by the autograph method on the surface of a flat electrode [11][12][13][14][15][16][17][18], then by shadow and interference methods of high spacetime resolution in the volume of the discharge gap [18][19][20][21][22][23][24][25]. Especially note that the microchannel structure against the background of the discharges glow was unresolvable by optical and electron-optical methods [19].…”

“…its realization in a narrow range of conditions. At the same time, the microstructure was found in many types of discharges: in diffuse form of discharges in the gap " rod−plane", " wire parallel to the plane" [11,14,15,18]; barrier and spark discharges in geometry " pin−plane" and in homogeneous gaps [12,[16][17][18][19][20][21][22][23][24][25]; in a streamerless discharge in a homogeneous gap [13]. Note, however, that all of these discharges are realized in air at atmospheric pressure.…”