Two-dimensional simulation of a direct-current microhollow cathode discharge

Abstract

Microhollow cathode discharges (MHCD’s) are miniature direct-current discharges that operate at elevated pressures (several tens to hundreds of Torr) with electrode dimensions in the $10–100\text{-}\mu \mathrm{m}$ range. MHCD’s have been proposed for a number of applications based on their unique characteristics such as presence of intense excimer radiation and significant gas heating within the submillimeter discharge volume. A two-dimensional, self-consistent fluid model of a helium MHCD in the high-pressure (several hundreds of Torr), high-current $(\sim 1\mathrm{mA})$ operating regime is presented in this study. Results indicate that the MHCD operates in an abnormal glow discharge mode with charged and excited metastable species with densities of $\sim {10}^{20}{\mathrm{m}}^{-3}$ , electron temperatures of approximately tens of eV, and gas temperatures of hundreds of Kelvin above room temperature. Significant discharge activity exists outside of the hollow region. The discharge volume and intensity increases with increasing current and becomes more confined with increasing pressures. Most predictions presented in this paper are in qualitative and quantitative agreement with experimental data for MHCD’s under similar conditions.