Suppression of the Ablation Phase in Wire Array Z Pinches Using a Tailored Current Prepulse

Abstract

A new wire array configuration has been used to create thin shell-like implosions in a cylindrical array. The setup introduces a $\sim 5\mathrm{kA}$, $\sim 25\mathrm{ns}$ current prepulse followed by a $\sim 140\mathrm{ns}$ current-free interval before the application of the main ($\sim 1\mathrm{MA}$) current pulse. The prepulse volumetrically heats the wires which expand to $\sim 1\mathrm{mm}$ diameter leaving no dense wire core and without development of instabilities. The main current pulse then ionizes all the array mass resulting in suppression of the ablation phase, an accelerating implosion, and no trailing mass. Rayleigh-Taylor instability growth in the imploding plasma is inferred to be seeded by $\mu \mathrm{m}$-scale perturbations on the surface of the wires. The absence of wire cores is found to be the critical factor in altering the implosion dynamics.