A hollow cathode neutralizer for a 30-cm diameter bombardment thruster

Recent improvements in overall thruster performance have imposed new constraints on neutralizer performance. The use of compensated grid extraction system requires a reevaluation of neutralizer position. A series of tests were conducted to determine what effect neutralizer cathode geometry has on performance. The parameters investigated included orifice diameter and length, and cathode diameter. Similar tests investigated open and enclosed keeper geometries. Neutralizer position tests with compensated grids suggested positions approximately 10 cm from the accelerator and radially out of the beam envelope should result in satisfactory performance and long life. Operation at keeper current of 1.5 am resulted in lower total neutralizer power, the elimination of tip heater power, and suitable closed loop control of the neutralizer vaporizer.