Application of vacuum arc cathode spot model to graphite cathode

A model of near-electrode processes is applied here to describe the behavior of cathode spots on graphite cathode in vacuum are. The physical model is based on a kinetic treatment of cathode evaporation, electron emission from the cathode, and plasma production. The model consists of physical assumptions and a system of equations that are formulated in the paper. Spot parameters, such as cathode erosion rate, cathode potential drop, cathode surface temperature, current density, electric field, and plasma density, temperature, and velocity in the near-electrode region are calculated numerically. The calculation includes the dependence of spot parameters on spot current and spot life time. The variation of spot parameters as a function of spot life time are very strong at life times shorter than 10 mu s. The calculations indicate that Joule heating in the cathode body is significant, and may exceed cathode heating by the ion heat flux, Calculated spot parameters are compared with the corresponding experimental data for relatively low are currents (<100 A) and their agreement is discussed.