Cathode spot division in vacuum arcs with solid metal cathodes

Studies of cathode spot division have been made for vacuum arcs with solid metal cathodes of zinc, lead, copper, aluminium and bismuth for discharge currents in the range 5-150 A. The distribution function of the number of spots is Gaussian for fixed experimental conditions. Above a certain current i0 the mean number of spots increases linearly with current except for bismuth. A model for spot splitting is proposed which is based on the energy balance at the cathode surface and temperature-field emission for electrons.