Analysis of anode surface roughness influence on heaterless hollow cathode discharge

Abstract

This research delves into the influence of cylindrical and planar anode surface roughness on heaterless hollow cathode discharge characteristics. Three surface roughness levels, Ra 1.6 µm, Ra 3.2 µm, and Ra 6.4 µm, along the cylindrical anode's azimuthal direction and the planar anode's radial direction, have been selected and modified by the machining process. A central finding is the correlation between the discharge voltage and anode surface roughness. As the roughness increases, cylindrical and planar anodes require less discharge voltage to sustain the primary discharge. This reduction is likely due to the enhanced surface area from the roughness, which aids in electron current collection. The discharge voltage oscillations appear inversely related to the surface roughness of planar anodes, which may be associated with changes in the neutral gas density gradient between the planar anode and the cathode. In contrast, cylindrical anodes show fewer effects from their surface roughness, likely due to the distinct neutral gas flow dynamics. These findings offer insights into standardizing hollow cathode testing and allow future research to explore these interactions more deeply.