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In order to understand plasma properties of hollow cathodes, a numerical simulation code with Hybrid-PIC model has been developed, in which ions and electrons are modeled as particles and fluid, respectively. In this study, as a first step, the applicability of the model is demonstrated, and then the influences of the emitter temperature on the flow field are discussed for a discharge current of 30 A and a mass flow rate of 1 mg/s. The electron density for the maximum emitter temperature of 1900 K agrees well with the experimental data from JPL. The results also show that the electron density tends to be higher with lower emitter temperature due to the higher electron temperature inside the cathode tube. The higher electron temperature is caused by the energy loss suppression resulting from the higher sheath voltage on the emitter surface. It was also found that charge exchange collisions shift the location of the electron density peak upstream.

Numerical simulation of plasma flow and the self-heating characteristics of a LaB 6 hollow cathode were performed using a hybrid-PIC model. For a discharge current of 30 A and mass flow rate of 3 mg/s, the influences of an emitter temperature profile and model parameter included in an anomalous resistivity model on the plasma flow and energy flux were investigated. In the simulation, the discharge voltage was fixed at a predetermined value and the maximum emitter temperature was periodically adjusted to keep the discharge current constant. The results show that the present model predicts the keeper floating voltage within an accuracy of 20%. It is found that the main reason for the emitter temperature to rise is due to ion bombardment and accompanying recombination energy, and that the maximum emitter temperature can be kept lower as the emitter temperature profile becomes uniform. It is also shown that thermal input into the emitter is decreased when anomalous resistivity increases.

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