Anode spot vacuum arc model: graphite anode

A model of near anode processes in vacuum arc anode spots on graphite electrode is developed. The physical model is based on a kinetic treatment of anode evaporation and plasma production. The system of equations formulated in the paper includes description of plasma flow in the kinetic and in the plasma acceleration regions in a self-consistent manner. Spot parameters, such as, anode surface temperature, current density, plasma density and temperature, plasma velocity in the near-electrode region and in region of plasma expansion are calculated numerically. The calculation includes the dependence of spot parameters on anode erosion rate, initial anode surface temperature and spot life time. The calculations indicate that Joule energy in the anode body is significant, and in some cases may exceed the anode surface energy source (difference between the electron energy flux and energy flux related to the anode mass loss). The anode erosion rate in vacuum arc can sufficiently differ from the anode material evaporation rate in vacuum obtained by Dushman formula.