Homogeneous electrical explosion of tungsten wire in vacuum

Experimental results on Joule energy deposition upon initiation of a fast electrical explosion of 16-μm tungsten wire in vacuum at current densities of more than 108 A/cm2 are reported. We have found that explosion with a fast current rise time (∼170 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 a value of up to ∼185 μΩ cm before surface flashover that significantly exceeds the melting boundary and corresponds to a temperature of ∼1 eV. The highest values for light radiation and expansion velocity of wire ∼1 km/s were observed for the fast explosion. For the explosion mode with a slower current rise time (∼22 A/ns into a short), we observed the existence of an “energy deposition barrier” for tungsten wire. In the 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 ∼120 μΩ 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 electron emission from the wire surface, which starts before melting.