Homogeneous electrical explosion of tungsten wire in vacuum

Experimental results on joule energy deposition at initiation of a fast electrical explosion of $16\mu$m tungsten wire in vacuum at current densities of more than $10^8$ A/cm$^2$ are reported. We find that explosion with a fast current rise-time ($\sim170\,$A/ns into a short) results in homogeneous and enhanced deposition of electrical energy into the tungsten before surface flashover. The maximum tungsten wire resistivity reaches the value of up to $\sim185\mu\Omega$ cm before surface flashover that significantly exceeds the melting boundary and corresponds to temperature of $\sim1\,$eV. The highest values for light radiation and expansion velocity of wire $\sim1\,$km/s have been observed for the fast explosion. For the explosion mode with a slower current rise-time ($\sim20\,$A/ns into a short)), we observe the existence of an «energy deposition barrier» for tungsten wire. At slow explosion mode the current is reconnected to the surface shunting discharge before melting. The maximum tungsten wire resistivity in this case reaches the value of $\sim120\,\mu\Omega\cdot$cm which is less than indicative of melting. Also the energy deposition along the wire is strongly inhomogeneous and wire is disintegrated into parts. We attribute the early reconnection of the current to the surface discharge for the slow explosion to high electronic emission from the wire surface, which starts before melting.