Central and External Cathode Operations in a Diverging-Magnetic-Field Electrostatic Thruster

摘要

The effects of hollow cathode position on thrust performances of a diverging-magnetic-field electrostatic thruster,which had a diverging magnetic field between a ring anode and a hollow cathode, were investigated. The hollowcathode was located in either a central or an external configuration. Based on the discharge current and direct thrustmeasurements, electrostatic and magnetic hybrid plasma acceleration was observed in the central cathode operationand even in the external cathode operation especiallywhen magnetic field strength was less than 315 mT. However, theoperating points were different: low discharge voltage × large discharge current in the central cathode operation,and high discharge voltage × small discharge current in the external cathode operation. This difference comes fromelectron-Hall parameter; the estimated electron-Hall parameter was about 50 in the central cathode operation, whichwas much lower than that of 3000 in the external cathode operation. By combining electromagnetic acceleration, thegenerated thrust can increase even with lower electron-Hall parameter operation. As a result, similar thrustperformances were achieved in both cathode positions. Because of the hybrid plasma acceleration method, thrustdensity reached 50 N=m~2, which is comparable or even higher than that of the conventional electrostatic thrusters.