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16Complex Systems of Charged Particles and their Interactions with Electromagnetic Radiation 2019
FORMATION OF IMPULSE DISCHARGE IN HELIUM OF HIGH PRESSURE V.S. Kurbanismailov1, S.A. Maiorov2,3, O.A. Omarov1, G. B. Ragimkhanov1
1Dagestan State University, Makhachkala, Russia, e-mail: gb-r@mail.ru
2Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia
Joint Institute for High Temperature of the Russian Academy of Sciences, Moscow, Russia
In this paper, an experimental study of the features of the formation and development of ionization luminescence fronts at the initial stages of breakdown, as well as physical processes causing the instability of a volume discharge in He at atmospheric pressure, was performed.
The studies were performed in short intervals (d = 1 cm), with a discharge area of s = 12 cm2 at voltages in the range from statistical breakdown (Ust = 6.8kV at d = 1 cm, p = 1 atm) to one hundred percent of overvoltage W = 194 % (up to 20kV) in a pre-ionized gas medium with a concentration of
8 3
pre-ionization electrons n0 ~ 10 cm .
The discharge under study was created between electrodes with a diameter of 4 cm and a radius of curvature of cm30 cm, separated from each other by a distance of d = 1 cm. The discharge was powered by high-voltage voltage pulses with adjustable amplitude up to 30 kV and the rise front ~ 10 ns generated by the generator pulsed voltages. Preliminary ionization of the gas was carried out by irradiating the gap with UV radiation from an external discharge, into which energy of « 0.3-0.4 J was deposited.
It is shown that in gas (not at atmospheric pressure), at small external fields (E0 <Ecr = 6 kV / cm) a homogeneous burns (photo 1), and the development of incomplete anodon-directed channels attached to cathode spots with high conductivity (plasma channels) began at a current density of ~ 40 A / cm2 (photo 3). In the interelectrode space, a good discharge plasma homogeneity was maintained. An increase in current density up to 60 A / cm (photo 4,5) leads to the further advancement of unfinished anodon-directed channels. At a current density of more than 100 A / cm2, the discharge gap overlaps the plasma channel (photo 6).
7(3kV)__2(7 kV) 5(10 kV)
¥(11 kV)
5(12 kV)
6(13 kV)
-3
Fig. Integral breakdown patterns in helium: d = 1 cm, p = 760 Torr.
7
With insignificant overvoltages W = 10-100% and pre-ionization electron concentration n0=10 cm , the formation of a plasma column occurs in the process and spreads to the cathode of the ionization wave with a speed of «2-5-10 cm / s.
THIS WORK WAS PARTIALLY SUPPORTED BY THE GRANT OF THE RUSSIAN FOUNDATION FOR BASIC RESEARCH NO. 19-08-00333A.
