Homogeneous electrical explosion of refractory metal wires in a vacuum

Summary form only given. The results on joule energy deposition at initiation of fast electrical explosion of W, Mo, Pt and Ti wires in vacuum at current densities of more than 100 MA/cm/sup 2/ are reported. Explosion with fast current rise-time (/spl sim/170 A/ns) results in homogeneous and enhanced deposition of electrical energy into the wire before surface flashover. The maximum tungsten wire resistivity reaches the value of up to 185 mcOhm*cm before surface flashover that significantly exceeds the melting boundary and corresponds to temperature of /spl sim/1 eV. The highest values for light radiation and expansion velocity of wire /spl sim/1 km/s have been observed for fast explosion. For explosion mode with slower current rise-time (/spl sim/20 A/ns), 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 120 mcOhm*cm which is less than indicative of melting. In addition, energy deposition along the wire is strongly inhomogeneous and wire is disintegrated into parts. Laser shadowgram,demonstrates local energy deposition into the wire at slow explosion mode. The early reconnection of current to the surface discharge for slow explosion of W wire might be due to high electronic emission from wire surface, which starts before melting. The value of deposited energy and its axial homogeneity arc improved with decrease of the substance atomization energy.