Erosion and Surface Morphology of the Graphite Electrodes in High-Current, High-Coulomb Transfer Gas Switch

Abstract

A two-electrode graphite gas switch has been widely used in power conditioning systems for high-power laser pumping due to its simple structure, robustness, and low cost. Previous studies have shown that the lifetime of the graphite gas switches mainly depended on the graphite erosion performance, while different types of graphite materials displayed a great difference in erosion performance. In order to understand the erosion mechanism of the graphite electrodes under high-current, high-Coulomb transfer working conditions, the electrode’s surface morphology was obtained during the lifetime experiments, and the thermophysical process on the electrode surface was studied. The results showed that the energy derived from arc plasma was mainly used for graphite sublimation, and the surface morphology of the graphite electrodes was obviously different. The reason could be that the heat flux on anode and cathode surfaces was different due to convection process generated by electron flow during discharge. The erosion rate of the anode was heavier than that of the cathode, and the proportion was around 2.15:1. The measured erosion rates of the electrodes were linearly increased with the number of discharges; this was significant for predicting the lifetime of the two-electrode graphite gas switch.