Ionization features in cathode spot region of vacuum arc

Abstract

A model of ionization processes in a low-temperature plasma within the cathode region of a vacuum arc is presented. This mathematical model is represented by a system of nonlinear differential equations of drift-diffusion for the electron density and the average energy of second-order electrons. The system of equations was solved by the finite element method in two coordinates in numerical form using the COMSOL Multiphysics software program. It was shown that due to nonequilibrium processes, Langmuir waves appeared at the plasma boundary, which leads to multistage ionization of metal vapor. The arc discharge was presented in the form of a cylindrical plasma column with a length of 200 μm and a diameter of 50 μm. At the interface between the cathode and the plasma column, a double electric layer has appeared which holds hot electrons in the central zone of the discharge. High specific power was focused close to the cathode surface, which provided the continuous supply of metal vapor. The numerical results of the model have appeared to be in good agreement with the experimental data.