Features of Cathode Sheath of Abnormal Glow Discharge in Helium: Probe Measurements

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 are investigated in the pressure range of 3.5–9 torr and the voltage range of 200–1700 V. The nonmonotonic behavior of the current–voltage characteristics is demonstrated under conditions minimizing controlled and uncontrolled impurities. It is shown that if the powers deposited into the discharge exceed 3.5 W, a deviation from the asymptotic approximation of the cathode fall length of the potential to a value of 0.37 of the normal length is observed, which is associated with a change in particle concentration in the 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 describing the kinetics of processes in high-voltage gas discharges used as sources of optical radiation.