Experimental Observations of Electrode Plasma-Surface Chemistry in Air-Breathing Gridded Ion Thrusters

Electrode surfaces inside air-breathing electric propulsion (ABEP) plasma discharges are exposed to reactive oxygen and nitrogen species which can form insulating layers and quickly degrade thruster performance. Previous literature has shown titanium and stainless steel both have potential for mitigating electrode surface degradation, but limited analysis of electrode surfaces was performed (Lotz 2013, Tejeda and Knoll 2023). In this work, stainless steel and titanium electrodes are tested in a radiofrequency (RF) gridded ion thruster running on nitrogen and oxygen. Surface layer growth and composition are analyzed via SEM and EDS imaging. Material recommendations which limit electrode performance degradation in ABEP thruster electrodes are made.