A cathode spot vacuum arc with graphite cathode

A theoretical study of near-electrode processes on graphite cathodes is presented. A physical model based on the kinetic treatment of cathode evaporation and electron emission from the cathode, as well as plasma production, is developed. A system of equations for calculating the electrode erosion rate and cathode potential drop as well the cathode surface temperature, current density, electric field and plasma density, temperature and velocity in the near-electrode region is described and solved numerically. The calculation show that Joule heating in the cathode body may be significant and can be exceed the cathode heating by the ion flux. The theoretically obtained values of the cathode erosion rate, plasma density and plasma electron temperature in range of spot current 5-70 A are in good agreement with such cathode parameters measured for relatively low arc currents (<100 A)