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

TLDR

The study experimentally demonstrates that higher current rise rates significantly increase energy deposition into the metal core of nanosecond exploding wires in vacuum before voltage breakdown. Fast current rise rates (20–150 A/ns) markedly increase energy deposition into exploding wire cores, as shown for nine metals, with tungsten showing the strongest effect, converting solid cores to cluster‑like states and delivering 1.5–2.9 times the atomization enthalpy for nonrefractory metals, while slower rates yield 2–3 times less energy, underscoring the importance of current‑rate control for wire ablation, mass reduction, and x‑ray yield in high‑current Z‑pinch experiments.

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.