Erosion Measurements in a Low-Power Cusped-Field Plasma Thruster

摘要

Results from a long duration test of a cusped-field plasma thruster operating at an anode power of 165 W are presented and discussed. Profile measurements of the boron nitride insulator were performed before and after the 204 h test, enabling the quantification of average erosion rates over a large portion of the interior. Unlike most Hall thrusters, the lifetime is not limited by erosion near the exit plane, due to the positioning of magnetic circuit elements. Additionally, the maximum erosion rate is found to be lower than rates measured in low-power Hall thrusters. The lifetime of this laboratory prototype is estimated at 920-1220 h based on the time needed to erode through the insulator in one of the ring cusps. However, as an indicator of the potential for cusped-field thruster designs to obtain longer lifetimes, the low erosion rate measurements are more significant. For example, fortifying cusps with additional or more durable material could increase lifetime. A summary of long duration tests and erosion measurements in Hall thrusters is also provided. During the tests discussed here, the thruster operated in the "high- current" mode, characterized by strongly oscillatory anode currents. Peak erosion rates are located upstream of the exit in this mode of operation. Reliable performance measurements were not acquired during this test, but anode current values suggest the thruster did not operate with the desired anode efficiency.