Structural evolution of flash-vaporized metal wire by modulated pulsed current

Understanding the evolution of electrical explosion products is with great importance in many fields such load design (Z-pinch), opening switch, nanomaterial preparation, etc. In this work, a Cu wire is vaporized by the elaborately-designed pulsed current, where the heating of exploding wire is stopped by a bypass branch. By doing so, the evolution of metal vapor itself can be observed without disturbance of luminous discharge plasma. High-speed photography along with electro-optical diagnostics reveal many physical details of the metal vapor. Morphologically, the exploding wire is dominated by electro-thermal instability which later coupled with Rayleigh-Taylor instability during the ~50 μs fast-expansion into ambient air. The stratified structure stabled for about 300 μs. The successive diffusion appears typical hydrodynamic instabilities, and detectable emission of the vapor lasts for ~5 ms. By adding a rigid wall in vicinity of the exploding wire, the structure of vapor is largely influenced. As a result, the rebounded explosion products enhance instability development significantly, and the protrusions can reach cm level. Finally, the electromagnetic radiation of the explosion process is monitored, which mainly comes from sudden change of current of the circuit.