Numerical study of light emission from a micro-hollow cathode discharge; the effects of different working gases

Abstract

This work addresses the ultraviolet, infrared, and visible light emissions from a micro-hollow cathode discharge operating at the self-pulsing regime. Three different gas mixtures, i.e., He–Xe, Ne–Xe, and He–Ne–Xe, are investigated. A volume-averaged approach with a comprehensive chemistry model is used to simulate the discharge. The effects of different gas mixtures, the total gas pressure, and the concentration of xenon atoms on the generation of different species, as well as on the light emissions, are carefully studied. The results show that the infrared efficiency of the micro-hollow cathode discharge is dramatically low (less than 0.001%), but its ultraviolet efficiency, with a maximum of 38% for a pure Xe discharge, is even higher than that of plasma display panels, which have a maximum of 35%. The ultraviolet efficiency of the Ne–Xe discharge is higher than that of the He–Xe at low xenon concentrations, whereas the reverse is true at higher concentrations. It is also found that there is an optimum pressure that maximizes the excimers’ densities and consequently the amount of ultraviolet radiation. The optimum pressure depends on the hole diameter of the hollow cathode structure. A comparison between different gas mixtures revealed that the ultraviolet efficiency of the He–Ne–Xe mixture at certain mixing ratios, e.g., 0.45He–0.45Ne–0.1Xe, can be much higher than those of He–Xe and Ne–Xe mixtures.