Experimental characterization of a low current thermionic dry neutralizer in an electron gun configuration for ion engines

Abstract A critical aspect of the development of next-generation electric propulsion systems for new deep-space small satellites and CubeSats is the neutralization system. Dry, or propellantless, neutralizers represent an attractive alternative to the conventional wet neutralization systems as a cathode current < 100 mA can be achieved with a low power input (< 20 W) with significant specific impulse savings, propellant system simplification and potential power savings. Using a validated 2D axisymmetric COMSOL Multiphysics model, a thermionic dry neutralizer based on an electron gun configuration has been designed, developed, and experimentally characterized. The experimental characterization in diode mode has investigated the influence on the cathode emission and system losses of the extraction electrode voltage and anode voltage respectively in the 100–580 V and 0–30 V range. Experimental results show good agreement with simulation predictions used in the design phase. The electric field focusing and space charge de-focusing effects to minimize power losses are discussed. Furthermore, the thermal influence of the emitter temperature is explored from 1110 $$\:^\circ\:$$ C to 1200 $$\:^\circ\:$$ C assessing the minimum operational power, poisoning effects, and thermal hysteresis. The neutralizer has achieved a maximum anode current of 55.8 mA at an extraction electrode biasing voltage < 600 V and a heater power consumption of 10.5 W, resulting in a total power-to-current ratio of 0.32 W/mA. Thus, technologically demonstrating emission and power characteristics suitable for thruster neutralization of small satellites and CubeSat applications.