Features of the cathode sheath in abnormal glow discharge in helium: probe measurements
G.V. Shevchenko1,2, P.A. Bokhan1, P.P. Gugin1, M.A. Lavrukhin1, D.E. Zakrevsky1,2
1Rzhanov Institute of Semiconductor Physics of the Siberian Branch of the RAS, Novosibirsk, Russia
2Novosibirsk State Technical University, Novosibirsk, Russia
Keywords: discharge, current-voltage characteristics, cathode potential drop, length, probe measurement, pure conditions, helium, cathode sheath, Townsend coefficient
Abstract
A gas discharge is an effective converter of electrical energy into optical radiation. The mechanisms of current development and the quantitative contribution of electron multiplication and emission processes remain undetermined, even in the simplest discharge types, such as the abnormal glow discharge. In this work, the current-voltage characteristics and the voltage distribution in the cathode sheath region of a DC discharge in helium were investigated in the pressure range 3.5-9 torr and the voltage range 200-1700 V. The non-monotonic behavior of the current-voltage characteristics was demonstrated under conditions minimizing controlled and uncontrolled impurities. It was shown that at powers deposited into the discharge exceeding 3.5 W, a deviation from the asymptotic approximation of the cathode fall length to a value of 0.37 of the normal length is observed, which is associated with a change in particle concentration in the near-cathode region. The derived empirical law made it possible to refine known approximations for the dependence of temperature and particle concentration on the power deposited into the discharge, which is relevant for description of the kinetics of processes in high-voltage gas discharges used as sources of optical radiation.
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