Investigation of the discontinuous change in the anode potential drop in a helium glow discharge with a cylindrical hollow cathode

Abstract

Experimental and numerical investigations of a DC glow discharge in helium, operating between a cylindrical hollow cathode and a flat anode, were conducted in a 25 mm diameter tube with a 25 mm interelectrode gap. Experimentally, it was found that at a gas pressure of 2.6 Torr, an intense glow appears near the anode surface, which intensifies with increasing pressure. Probe measurements of the potential between the anode and the probe revealed a sharp potential drop when the pressure increased from 2.4 Torr to 2.6 Torr. Numerical calculations showed that as the gas pressure rises, the excitation reaction rate of the helium resonant level decreases in the interelectrode space, but increases near the anode. At a pressure of 4 Torr, the excitation reaction rate at the anode surface becomes an order of magnitude higher than in the region between the cathode and anode. Additionally, the numerical calculations indicated that under the conditions considered, the electric field near the anode is always positive, leading to a positive anode potential drop.