Undrodynamic instability of exploding wires

Exploding wires are used for a variety of pulsed power applications, like soft x-ray generation in imploding liners, as opening switches in high voltage generation, for thin film coating and nanopowder production, and as protective fuses in high current applications. In many cases, the hydrodynamic instability of the wire prior to the complete deposition of the electrical energy of the driving pulse leads to detrimental effects, very often adversely influencing the process. In this work, we report on the direct visual observation of the onset of magneto-hydrodynamic (MHD) instabilities of tin (Sn) wires exposed to 100 MW/cm² pulses of up to several milliseconds duration. A high-speed, high resolution video camera is used to visualize the dynamical behavior of the wire under such a load. Numerical simulation of the electrical circuit, and a simple one-dimensional model are used to explain the observed behavior. The theory shows a satisfactory agreement with the experiment, not only qualitatively but also on a quantitative scale, in particular in regard of the onset of the MHD instability. The preferred instability is m=0 mode, leading to a premature pinch-off of the wire at multiple locations almost simultaneously