Cathode position effects on microwave discharge cusped field thruster

The microwave discharge cusped field thruster is a novel concept of electric micropropulsion device, which operates μN level thrust in low mass flow rate conditions, making use of a coaxial transmission line resonator. With its advantages of low thrust noise and high thrust resolution over a wide range of thrust, the thruster has emerged as a candidate thruster for the space-borne gravitational wave detection mission. The cathode effects commonly exist in many kinds of electric propulsion, and they are typically significant in micropropulsions. In order to find out the cathode position effects on a microwave discharge cusped field thruster, a thermionic cathode is mounted on a cross-slider for coupling. Under different cathode positions, the plume is analyzed by a Faraday probe and a retarding potential analyzer to analyze the performance and discharge characteristics. The results show that the magnetic mirror effect leads to significant degradation of anode current and an increase in low-energy ion ratio as the cathode moves away from the thruster exit. The electron conduction route also significantly impacts anode current efficiency, related to the cathode-exit distance and the thruster magnetic topology.