Use of kinetic simulations for the determination of particle and energy fluxes at the cathode surface of a vacuum arc

摘要

A kinetic model and the associated PIC-MCC numerical technique have been used to simulate the plasma generated by a vacuum arc cathode spot fragment and calculate the current densities and net energy fluxes at the cathode surface. The model is based on a comprehensive description of the plasma generation processes, including a detailed representation of metal vapor particle ionization and plasma-cathode interaction. An important feature of this model is its ability to provide details of the spatial variations of plasma parameters within the near cathode region. Calculations are carried out for nickel, titanium and zirconium cathodes as a function of the surface temperature. It is found that below a threshold surface temperature the energy input to the cathode is negative and the spot fragment can not operate in a self-sustained way. The relative importance of the different mechanisms controlling current and energy transfers at the cathode surface are analyzed in detail.