Study on neutralization and degradation characteristics of the cathode of tungsten in microwave ion thruster

With the increasing demand for high-performance electric propulsion in micro-nano satellites, the cathode of tungsten has become an ideal neutralizer solution. However, its neutralization characteristics and performance degradation mechanisms in a coupled environment remain unclear. In this study, a coupled cathode-thruster experimental system is constructed to systematically investigate the neutralization characteristics and performance degradation mechanisms. The results show that a “keeper critical voltage” related to the heating power exists; operation below this value triggers neutralization deterioration. This critical voltage exhibits a linear negative correlation with the tungsten filament temperature, validating the “thermionic-field complementary” emission mechanism of the cathode. Long-term experiments indicate that the performance of the cathode of tungsten continuously degrades over time during long-term coupling. Surface analysis confirms that carbon deposition is the primary form of contamination, while a positive feedback effect between coating loss and carbon contamination accelerates the performance degradation process. This study reveals the neutralization characteristics and degradation mechanisms of the cathode of tungsten in a coupled environment, providing theoretical basis and experimental support for the reliable design and lifetime assessment of micro electric propulsion systems.