Effect of current rate on energy deposition into exploding metal wires in vacuum

Abstract

This paper presents direct experimental proof of a significant increase of energy deposition into a metal core before voltage breakdown with the current rate for nanosecond exploding wires in a vacuum. This effect is demonstrated for nine different refractory and nonrefractory metals. The strongest influence of current rate was demonstrated for tungsten wires. Increasing the current rate from 20 to 150 A/ns changes the wire core from a solid to a cluster-like state. For nonrefractory metals such as Ag, Al, Cu, and Au, fast explosion allows deposition inside a metal core 1.5–2.9 times the atomization enthalpy before voltage breakdown. The slow explosion, with 20 A/ns, gives 2–3 times less energy deposition before voltage breakdown than the fast-explosion mode. The current-rate effect is important for optimization of wire ablation, reduction of the mass left behind in the wire-array load, and final x-ray yield in modern multi-MA wire-array Z-pinch facilities.