Effect of deposited energy on the structure of an exploding tungsten wire core in a vacuum

The experiments demonstrate the full range of transformations of an exploding tungsten wire core from a solid state to total vaporization. These states are correlated with the value of deposited energy before voltage breakdown. If the deposited energy is less than the solid-state enthalpy, the wire remains solid. If the deposited energy is between the solid- and liquid-state enthalpy, the wire disintegrates into solid macroscopic-sized pieces. If the voltage breakdown happens during the liquid state, the wire expands. In this case, the expansion velocity of the wire (0.1-1 km/s) is almost a linear function of the deposited energy. The expanding wire core is homogeneous for a deposited energy more than 4 eV/atom and nonhomogeneous (100-200 mu m scale spots) for deposited energy less than 4 eV/atom. For homogeneous expansion, the wire core consists mainly of hot liquid microdrops of submicron size [G. S. Sarkisov, P. V. Sasorov, K. W. Struve , J. Appl. Phys. 96, 1674 (2004)]. For deposited energy higher than atomization enthalpy, the wire core transforms into the gas-plasma state. The linear dependence between deposited energy and expansion velocity for W wires was demonstrated. The data presented are important for the optimization of the ablation rate of wire arrays in modern high-current Z-pinch installations. (c) 2005 American Institute of Physics.