A Study of the Motion of High-Energy Electrons in a Helium Hollow Cathode Discharge

Abstract

Abstract The motion of high-energy electrons was studied in a helium hollow cathode discharge using Monte Carlo simulation. The calculations were carried out in the pressure range of 2-10 mbar. The length of the cathode dark space (CDS) was determined by simulation in an iterative way using experimental voltage-current density characteristics of the discharge. At the lowest helium pressure (2 mbar) the concentration of high-energy electrons was found to be the same at the CDS-negative glow boundary and at the midplane of the discharge while at 8 mbars it was found to be by 1-2 orders of magnitude smaller. The results of our calculations support the existence of "oscillating" electrons. The probability of 1, 2 and 3 transfers through the negative glow (NG) for primary electrons was found to be 37%, 11 % and 2%, respectively, at 2 mbar pressure. The spatial distribution of ionizations and the angular distribution of electron velocity at the CDS-NG boundary were also investigated. The pressure dependence of the current balance at the cathode was obtained, and the results indicate that with decreasing pressure other secondary emission processes than ion impact become important in the maintenance of the discharge.