Plume Characterization of an Ion-Focusing Hall Thruster

The T-220HT Hall-effect thruster is modified to include in-channel electrodes and additional magnetic coils to study ion focusing. The goal of this work is to decrease energy losses from ion-wall neutralization and plume divergence to increase the thrust-to-power ratio. In this paper, thrust and plume measurements on xenon are presented. The thruster was tested from 125 to 300 V at 9 A discharge, with the electrodes either floating or biased to 10 or 30 V above anode potential. The mass flow rate was varied from 9.8 to 10:4 mg=s to maintain constant discharge current. The maximum operating chamber pressure was 7:7 10 6 Torr-Xe. Performance measurements on xenon show the best overall increase in performance at 150 V discharge and 10 V electrodes with an increase of 7.69 mN of thrust, 4:6 mN=kW thrust-to-power ratio, 123 s ISP, and 5.3% anode efficiency. The plume ion energy distribution function indicates an ion energy increase up to 25 V. The ion number density and propellant efficiency both show increases. The different electrode currents and ion energy distribution functions at 10 V compared with 30 V electrodes suggest different electrode-plasma interaction at the two electrode biases.