The relationship between exploding wire expansion rates and wire material properties near the boiling temperature

The energy deposited by a submicrosecond, ∼1-kA current pulse in a 25-μm diameter metal wire prior to its explosion, correlates directly with the expansion rate of the wire after the explosion. Energy deposition by resistive heating is terminated by the formation of plasma around the wire and a collapse of the voltage along the wire, and is evidently facilitated by the desorption of gases from the wire and/or the evaporation of the wire material (or impurities within it) as it heats up. Data presented here implies that the relationship between materials with the lowest resistivities and high exploding wire expansion rates found in earlier work (D. B. Sinars et al. 2000) is a result of the reduced voltage delaying the gas breakdown along such wires. This, in turn, increases the energy deposited resistively in the wire before the current shifts to the surrounding plasma. If gas breakdown does not occur until close to the full vaporization energy is deposited in the wire, the expansion rate will be more rapid than if a small fraction of the vaporization energy is deposited before voltage collapse.