Characterization of Hollow Cathode Performance and Thermal Behavior

Hollow cathodes play a crucial role in the functioning of ion engines and Hall thrusters, where their performance and longevity are critical for successful missions. This study aims to characterize the performance and thermal behavior of various hollow cathode technologies, especially focusing on their potential to meet the demands of future deep-space missions. We investigated three alternate hollow cathode technologies that utilize different emitter materials and geometries to overcome limitations found in current systems. Performance measurements were conducted on impregnated tungsten-iridium dispenser cathodes across discharge currents ranging from 4 to 15 A, revealing that these cathodes maintain the same operational range and ion production efficiency as traditional tungsten dispensers. Temperature assessments indicated similar emitter temperatures for tungsten-iridium designs, but they did not demonstrate the expected decrease in work function at the tested current densities. Additionally, hollow cathodes utilizing lanthanum hexaboride emitters were evaluated, showcasing a wider operational current range but lower ion production efficiency below approximately 12.4 A due to increased heating requirements. A simple model elucidates the observed differences in operating voltages and ion production rates based on cathode parameter impacts on discharge behavior.