Development and Validation of Simplified 1D Models for Hollow Cathode Analysis and Design

Abstract

Several space electric propulsion devices, such as ion engines and Hall effect thrusters, use hollow cathodes as the electron sources for providing the necessary electrons for the ionization of the propellant and to neutralize the ion beam leaving the thruster. Since cathode performance is strongly tied with its geometry and size and plasma diagnostics is very difficult to be performed, simple numerical tools are required in order to determine optimal geometries and operative conditions for a given mission profile. The paper presents a preliminary design tool for orificed hollow cathodes. Two physical models compose the tool: a plasma model and a thermal model. A time-independent, volume-averaged model has been developed to determine plasma properties in the emitter and orifice regions. A Lumped Element Thermal Model has been also developed to compute temperature distributions and the respective gradients within the main cathode’s element. The study, conducted to validate the results of the models, shows that there is a good agreement with values and trends found in the available literature. The tool is able to estimate performances of new devices by the calculation of cathode working conditions for different geometries given device operating condition and insert material.