Experimental Study on Electrical Explosion Behavior of Six Metal Wires in Air and Vacuum

Experimental investigations have been carried out to establish a correlation of energy coupling efficiency in fast electrical explosion of different metals with known electrical and thermophysical properties. To cover a wide range of metal properties, in the present study, five metals (Au, Cu, Al, W, and Ti) are considered from two well-known groups (refractory and non refractory) and palladium is included as sixth metal having intermediate properties between these two. Comparative study is carried out for the same circuit parameters (current rate $\approx 90 \times 10^{9}$ A/s) to explore electrically exploding wire (EEW) behavior of these metals in two different media: air and vacuum. Temporal evolution of self-emitted light around these metal wires is analyzed as a qualitative measure for energy diversion from the metal core to outer corona and is recorded using streak camera for both media. In air, refractory and non refractory metals are seem to exhibit different behavior as inferred from voltage profiles, time of burst, temporal optical emission profiles, and overheating factor (the ratio of energy deposited till burst to the enthalpy of atomization). Overheating in air is found to depend inversely on the enthalpy of atomization and resistivity for refractory and non refractory metals, respectively. Pd has shown mixed electrical and optical characteristics of both groups (refractory and non refractory) in air as well as in vacuum. On changing the surrounding medium from air to vacuum, overheating is found to decrease for all metals; interestingly, their drop is observed to depend on the speed of sound at room temperature in that particular metal. Using these experimental outcomes, the possible mechanisms responsible for energy diversion in the explosion of wires of different materials along with their correlation to surrounding medium are discussed in this work. In the present study, the electrical characteristics of gold have been found to be most favorable for efficient energy coupling and hence for high-energy-density applications irrespective of the surrounding medium.