Model of the Formation of Liquid-Metal Jets in the Cathode Spot of a Vacuum Arc Discharge

The formation of jets is studied during the extrusion of a melted metal by the plasma pressure from microcraters formed in the cathode spot of a burning vacuum arc. An analytic model of liquid-metal splashing is proposed. At the initial stage, a axially symmetric liquid-metal wall is formed around the crater. Its radius is determined by comparing the rate of liquid extrusion from a forming crater and the Taylor-Culick velocity of the reverse motion of the toroidal rim of a liquid-metal wall. At the developed stage, the motion of liquid metal loses axial symmetry, which corresponds to a tendency to jet formation. According to the proposed model, this is due to the development of the Plateau-Rayleigh instability of the rim. The basic spatial and temporal parameters of the jet formation process are calculated.