Ionization, Plume Properties, and Performance of Cylindrical Hall Thrusters

It is shown experimentally that the cylindrical Hall thruster (CHT) produces a highly ionized plasma flow with mass utilization efficiencies greater than 100% due to generation of multicharged ions. For the CHT employing geometries with and without a short annular section, used to enhance ionization, plume divergence reductions of approximately 25% were demonstrated by running a cathode-keeper discharge along with the main cathode-anode discharge. Thruster anode efficiencies varied from approximately 15% to 35% over input powers from 70 to 220 W. A 2-A keeper discharge resulted in an approximately 20% increase in anode specific impulse for both geometries, and the specific impulse for the case of no annular section was, on average, 13% higher than that with the annular section. The multicharged ion fraction increased with keeper current, and the quantity of channel erosion products in the plume was correlated with that of multicharged ions.