Numerical Simulation of Time Evolution of Cathode Sheath Voltage Contributing to Evaporation of Fe Cathode in Vacuum Arc

It has been required to elucidate physics of cathode spots in vacuum arc in order to control it for industrial applications. The cathode spots in vacuum arc moves at high speed with evaporation from cathode metal caused by ion heating. The ion bombardment, which is the heating factor of the cathode, occurs when ions generated from the thermal plasma are accelerated in the cathode sheath and bombard the cathode. This heating is considered to cause the cathode to melt and evaporate, forming a new plasma spot. Since the cathode sheath voltage depends on the behavior of the plasma and the amount of electron emission from the cathode, it is considered that spatial distribution and variation with time of cathode sheath are formed. However, few papers have been quantitatively researched. In this research, it was constructed that numerical simulation based on electromagnetic thermodynamic fluid analysis coupled with an analysis of the electrostatic field in the cathode sheath. The analysis of electrostatic field in the cathode sheath was computed based on the Poisson's equation. Using this simulation model, it was analyzed that the spatial and time evolution in the cathode sheath voltage distribution contributing to the evaporation of the cathode metal.