Accelerated erosion of keeper electrode during coupling discharge between Hall thruster and hollow cathode

In this paper, keeper erosion of hollow cathode was found to be significantly accelerated due to the presence of divergent plume from Hall thruster. The results retrieved from multiple Retarding Potential Analyzers (RPAs) located at different positions near the exit of an HET-80 Hall thruster show that, aside from the 50–100eV ions produced near cathode exit due to ionization and associated instabilities, there exist 200–300eV incoming ion fluxes from thruster exit due to plume divergence, which will increase the equivalent sputtering yield of keeper material by 2.5–6.7 times and significantly shorten keeper lifetime. The result revealed a potential conflict between performance and lifetime when optimizing cathode location onboard Hall thrusters.