Plasma and Gas-Dynamic Near-Electrode Processes in the Initial Phase of a Microstructured Spark Discharge in Air
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and Gas-Dynamic Near-Electrode Processes in the Initial Phase of a Microstructured Spark Discharge in Air K. I. Almazovaa, A. N. Belonogova, V. V. Borovkova, V. S. Kurbanismailovb, G. B. Ragimkhanovb*, A. A. Tren’kina, D. V. Tereshonokc, and Z. R. Khalikovab a All
Russia Research Institute of Experimental Physics, Russian Federal Nuclear Center, Sarov, 607190 Russia b Dagestan State University, Makhachkala, Dagestan, 367000 Russia c Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412 Russia *e-mail: [email protected] Received April 14, 2020; revised April 20, 2020; accepted April 20, 2020
Abstract—The results of studies of the dynamics of near-electrode processes in the initial phase of a spark discharge in atmospheric-pressure air in the point-plane geometry are presented. After breakdown, regions of about 50 μm or more in size with an increased electron concentration of (3–8) × 1019 cm–3 near the surface of the flat cathode have been observed. With allowance for the experimental data on erosion effect of the discharge on the surface of a flat electrode and the associated gas-dynamic effects, a physical model of nearelectrode processes has been proposed, based on which the gas-dynamic parameters are estimated. Keywords: gas discharge, microstructure, near-cathode plasma, shock wave. DOI: 10.1134/S1063785020080039
Widespread practical application and scientific interest are making studies of pulsed gas discharges pertinent, resulting in a large number of publications in this area. Moreover, a number of phenomena are still poorly understood. One of them is associated with the presence of microstructure of the channels of current and its participation in gas-discharge processes in dense gases, when the channel is a cluster of about 100 or more channels of micron diameter [1–9]. The microstructure of the discharges was recorded by the method of autographs in the form of multitude microcraters on the surface of electrodes [1–5] and by the method of shadow photography in the volume of discharge gap [6–9]. In this case, the internal structure of the channel of current against the background of a luminous outer shell was not resolved by optical and electron-optical methods [1, 2, 4]. The data on microstructured discharges in dense gases obtained to date, first, indicate that this phenomenon is not rare and, second, indicate the possibility of a significant relationship between the microstructure and dynamics of the processes (see [1–8] and references therein). Thus, in studies of shadow photographing of a spark discharge near the surface of a flat electrode, semi-ring-shaped structures identified with hemispherical shock waves (SWs) were observed. It was suggested that the sources of SWs are the processes of microcrater formation in the areas in which microchannels are in contact with a flat electrode [5, 7]. In
this case, erosion microcraters had a diameter of 5‒35 μm and a depth of 0.1–0.4 μm [5]. The aim of this work is to continue the study of the dynamics of near-electrode processes in th
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