Mechanism of electrode surface damage and material removal in high current discharges

A model of surface damage and material removal is given based upon magnetohydrodynamic phenomena occurring at high current arc electrodes in the microsecond time regime, Experimental observations of the sudden increased erosion rate and surface damage above 250 kA indicate that molten electrode material begins to be driven into jets which break up into droplet streams. Macroprotrusions or "buttes" form by subsequent freezing of the jets which in turn arise from the collective interaction of individual arc filaments. This mechanism has been developed from a model of arc damage due to single filament discharges in the nanosecond time regime. The Stefan problem is considered with Ohmic heating of a liquid metal pool from which material is driven in a hydromagnetic flow. Alternate models of the liquid jet formation are investigated.