Effect of the temperature of an electrode microprotrusion on the microcrater formation on the electrode surface upon pulsed and radiofrequency vacuum breakdowns

The formation of a microcrater on the surface of an electrode as a result of the explosion of a microprotrusion caused by pulsed and radiofrequency vacuum breakdowns was numerically simulated to elucidate how the microprotrusion temperature affects the process. It has been shown that when the microprotrusion temperature is close to the melting point, a zone with an elevated temperature occurs in the center of the microcrater, where the material is in a liquid or a mixed (liquid plus gas) state. Within a certain time after the explosion of the microprotrusion, this zone propagates with high velocity into the bulk electrode. The result is the formation of a micrometer-sized crater with a cylindrical cavity in its central part. Microcraters of this type, usually formed on electrodes subjected to vacuum breakdowns, are also observed on electrodes exposed to laser, beam, and plasma pulsed energy deposition.