Diameter and Current Density of Single and Multiple Cathode Discharges in Vacuum

The diameter of craters formed by a vacuum discharge on a copper cathode was determined for single and multiple discharges in the current range of 4-230 A. For a fixed current the crater diameter has values according a lognormal distribution solely determined by the current. Current chopping is characterized by the, forming of craters having one specific diameter (3,6 μm). After splitting of a discharge the current is on the average equally divided over the partial discharges. The surface geometry influences the movement of the metal vapour discharge over the cathode, it does not affect the distribution of cratersizes. The most probable current density in the cathode plane is a function of the current and is in the order of 108 A/cm2.