Space–time parameters of the formation of a cathode crater during the operation of a cathode spot cell in a vacuum arc

Abstract

An experiment was performed to estimate the diameters and formation times of the craters formed during the operation of a cathode spot cell in a vacuum arc. The obtained experimental data and the relevant data available in the literature are analyzed within the framework of a two-dimensional axisymmetric model developed to investigate the crater formation on a cathode, which takes into account the finite lifetime of the cathode spot cell. The model is described by the Navier–Stokes equations for a viscous incompressible fluid with a free surface and the heat conduction equation taking into account convective heat transfer. The parameters of the interaction of the cathode spot plasma with the cathode surface are chosen in the process of simulation based on an analysis of experimental data on the parameters and mechanism of crater formation. The changes in the cathode shape caused by the motion of the molten metal under the action of the plasma pressure are calculated from the onset of melting. As a result of the simulation, the main geometric parameters of a crater (diameter and depth) and their formation time have been estimated as functions of the lifetime of the cathode spot cell.