Effects of cathode operating parameters on the ignition voltage threshold of Hall thrusters

Changing the operating parameters of a cathode affects the ignition process of a Hall thruster mainly by changing the micro-plasma parameters emitted by the cathode at the moment of ignition. However, the micro-plasma parameter that dominates this effect is not clear. Therefore, the ignition voltage thresholds with different cathode operating parameters were first measured. Then, to better understand how these operating parameters affect the ignition voltage threshold of a Hall thruster, the two-dimensional distribution characteristics of the electron density, electron temperature, and plasma potential in the cathode plume region were measured using a Langmuir probe. The results showed that increasing both the keeper current and mass flow rate of the cathode causes an increase in the electron density emitted by the cathode and a decrease in the electron temperature. It was also found that increasing the cathode mass flow rate has a more pronounced effect than increasing the keeper current. Furthermore, when both the mass flow rate and keeper current of the hollow cathode are increased, the ignition voltage threshold of the Hall thruster decreases significantly. This is mainly because of a significant increase in the electron density resulting from the increases in the mass flow rate and keeper current.