Design of Miniature Ring-Cusp Ion Thrusters via Analysis of Discharge EEDF and Plasma Parameter Mapping

摘要

An experimental effort was under taken to understand and improve the discharge efficiency of the Miniature Xenon Ion (MiXI) thruster. Analyses were performed on the 3 cm discharge with a 3-ring and 5-ring cusp configurations, which lead to a new axial ring cusp design that shows considerable promise. For each configuration, a Langmuir probe was used to make 2D maps of the electron energy distribution function (EEDF) and other important plasma parameters throughout the discharge chamber. For the standard ring-cusp configurations, the results show that the plasma structure is dominated by the cusp fields at the miniature scale and suggest that primary electron loss to the walls likely dominates discharge losses at this scale. The insight derived from the testing of the ring-cusp configurations led to the development of a new design approach: the Miniature Axial Ring Cusp Ion (MARCI) prototype thruster. Discharge mapping and performance testing of the MARCI discharge demonstrate favorable plasma conditions within the discharge and near the extraction plane, and that the device can potentially achieve discharge losses and mass utilization efficiencies near 245 W/A and 0.89, respectively. As such, the new MARCI design approach may allow miniature ion thrusters to achieve the performance and efficiency levels of highly efficient conventional ion thrusters.