Erosion and the origin of charged and neutral species in vacuum arcs

Erosion measurements on copper cathodes show the erosion rate to be dependent on different variables, such as arc current, arcing time and cathode size. The experimental results offer an explanation of the large variation in erosion rate values as found by earlier experiments. The behavior of other cathode metals proves to be similar. An analysis shows the variation in erosion to be caused by changes in the output of neutral species. It is concluded that ions and neutrals differ in origin of generation, the cathode spots being the centres of fully ionized metal vapour, while neutrals are formed in surrounding areas.