Corona-free explosion of the coated tungsten wires in vacuum

Summary form only given. The first experimental evidence of corona-free nanosecond electrical explosion of polyimide-coated W wire in vacuum is presented. Fast current raise /spl sim/150 A/ns and 2 /spl mu/m polyimide coating is important to achieve this regime of explosion. Relatively slow energy deposition or absent of appropriate wire coating results in generation of the plasma shell and voltage breakdown. In this case, the deposited energy restricted by value of /spl sim/10 eV/atom due to early termination of energy deposition. For corona-free explosion, wire remains resistive all time, voltage breakdown is absent and total deposited energy reach anomaly-high value of /spl sim/200 eV/atom. Expansion velocity increases from 0.5-1 km/s for uncoated wire to 2.5-4 km/s for coated one. Light emission from expanding wire core transformed from cluster-type radiation to the gas-plasma type. The main features of corona-free explosion of wire are reproduced by 1D MHD simulation. This experiments show new possibilities to create high-density and high-temperature plasma column using electrical explosion of single wire. The discovered phenomena can be useful for high-current wire array z-pinches to eliminate precursor plasma on axis and realize zero-D compression trajectory.