Modeling on plasma energy balance and transfer in a hollow cathode

摘要

The hollow cathode lifetime is largely determined by the dissipation of the active emitter material and the ion-induced sputtering erosion. These two critical factors are involved in the physical mechanisms of the internal energy balance and plasma energy transfer to the cathode walls. Based on particle kinetic dynamics and behaviour statistics, a plasma energy balance and transfer model for the hollow cathode was established. The hollow cathode discharge process and steady-state plasma parameters were investigated by employing the self-consistent full particle-in-cell approach combined with Monte Carlo collisions. Relevant 2D numerical simulations for the partially ionized gas in hollow cathode were performed. The calculated parameters of the plasma energy balance and transfer model mainly include the plasma potential, plasma density, particle velocity, resistivity distribution, ohmic heating and electric-field work. In the full particle-in-cell code, the hollow cathode operated at a planar diode regime with a discharge current of 10.0 A and a gas flow rate of 3.5 sccm. The simulation results show that the electric field power is 85.9 W in the insert region, 37.5 W in the orifice region and 147.4 W in the plume region, respectively. The work performed by the electron pressure gradient in the insert region, orifice region and plume region is in the ratio of about 1.2:1:5.3. The ion kinetic-energy flux is negligible compared with the electron kinetic-energy transfer.