Cathode position effects on microwave discharge cusped field thruster

Abstract The microwave discharge cusped field thruster is a novel concept of electric micro propulsion device, which operates μN level thrust in low mass flow rate conditions, making use of a coaxial transmission line resonator (CTLR). With the advantages of low thrust noise and high thrust resolution over a wide range of thrust, the thruster becomes a candidate thruster for the Gravitational Wave detection mission. The cathode effects commonly exist in many kinds of electric propulsions, and they are typically significant in micro propulsions. In order to find out the cathode position effects on microwave discharge cusped field thruster, a thermionic cathode is mounted on a cross-slider for the coupling. With cathode position varies, the plume is analyzed by a Faraday probe and an RPA 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.