Ion-induced electron emission cathode for a micro-newton HEMP thruster

Abstract

An ion-induced electron emission cathode is applied for the first time in micro electric propulsion devices. In this investigation, ion-induced electron emission is operated on an annular LaB6 emitter for the neutralization and ion extraction of a microwave discharge HEMP Thruster (High Efficiency Multi-staged Plasma Thruster). A plume plasma diagnosis is performed with a Faraday probe and a retarding potential analyzer to analyze the discharge characteristics and plasma parameters. The results show that the ion-induced electron emission cathode can provides an emission current of over 0.4 mA. Compared with the condition with a thermionic cathode, there is a reduction in the thruster extracted ion current due to the deficiency of the emission current. The emission current shows different trends over anode voltage in different position configurations, which are affected by the incident ion flux and ion energy. Since the ion-induced electron emission cathode is free of power supply and propellant, it is of significant potential for low-power electric propulsion systems.