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

Abstract

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 hollow cathode was located in either a central or an external configuration. Based on the discharge current and direct thrust measurements, electrostatic and magnetic hybrid plasma acceleration was observed in the central cathode operation and even in the external cathode operation especially when magnetic field strength was less than 315 mT. However, the operating points were different: low discharge discharge current in the central cathode operation, and high discharge discharge current in the external cathode operation. This difference comes from electron-Hall parameter; the estimated electron-Hall parameter was about 50 in the central cathode operation, which was much lower than that of 3000 in the external cathode operation. By combining electromagnetic acceleration, the generated thrust can increase even with lower electron-Hall parameter operation. As a result, similar thrust performances were achieved in both cathode positions. Because of the hybrid plasma acceleration method, thrust density reached , which is comparable or even higher than that of the conventional electrostatic thrusters.