Quantitative Measurements of Wire Ablation in Tungsten $X$-pinches at 80 kA

This paper investigates the ablation of wires in two-wire tungsten $X$ -pinches driven by an 80-kA current over 50 ns. High-resolution imaging using a Nomarski interferometer allows measurements close to the $X$-pinch cross point, where the ablation “flare” structure is observed to clearly develop during the drive-current rise time. Electron density profiles are recovered as a function of both distance normal to the wire and of time. Results compare favorably to the rocket model of wire ablation. In addition, the density contrast over the ablation “stream” and “gap” structure is measured and compared to similar measurements made using quantitative radiography on the 1-MA 250-ns MAGPIE generator at Imperial College London, London, U.K.