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

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.

Modelling of low-current self-generated oscillations in a hollow cathode discharge

“…It is noted that in the abnormal glow regime-when the cathode sheaths are well developed-the electrode arrangement allows the buildup of the hollow cathode effect: high-energy electrons can oscillate in the potential well formed between the cathode surfaces [27,28]. The hollow cathode effect significantly enhances the ionization rate thus playing a central role in the ionization balance of the discharge [29,30].…”

Monte Carlo analysis of the electrons' motion in a segmented hollow cathode discharge

“…As ε, and therefore σ , does not change between collisions, the integration of equation ( 2) can be carried out analytically and s 1 can be easily calculated. Electron energy distributions [13], the number of oscillating electrons and spatial distribution of the ionization have been calculated [14] in previous Monte Carlo studies of the electrons' motion in plane parallel hollow cathodes. These simulations and the simulation of electrons' motion in a cylindrical hollow cathode discharge [15] have utilized the null-collision technique to increase the computational speed [12,16].…”

Hybrid model of a plane-parallel hollow-cathode discharge

“…S(x, r) = I e(1 + 1/γ ) V xr N xr N 0 (14) where N xr is the number of ions (slow electrons) created in a cell with V xr volume around x and r. In the iterative solution of the fluid and MC models the γ coefficient was adjusted in a way that the calculated current converged to its experimental value. The typical integration time step in the fluid model was of the order of 10 ns; the MC part was usually run after 100 steps in the fluid model.…”

“…At high pressures the so-called micro-hollow-cathode discharges are also used as high-intensity light sources [5,6], while other HC configurations (at low pressures) have switching applications [7,8]. Because of their importance in these applications, HC discharges have been extensively investigated in the past decades experimentally and by means of modelling methods [9][10][11][12][13][14][15].…”