Optical measurements of the properties of exploding wires

Summary form only given. The explosions of fine wires driven by a pulsed current source with a rise rate of 10/sup 10/ A/s per wire were observed with optical diagnostics using a Nd:YAG laser [λ=532 nm, 4 ns]. Three simultaneous schlieren channels and two interferometry channels separated by 50 ns were used. The schlieren channels consist of a bright-field iris, a dark field strip and a dark-field knife-edge. The interferometry was performed using a new version of a shearing interferometer, which is based on a double-prism with an air wedge. The expansion rates of various materials (Cu, Ag, Au, etc.) both with and without thin insulating coatings were measured. A strong effect of the insulation coating on wire expansion was observed for all those materials (Sinars et al., 2000). The interferometry images showed a plasma shell surrounding an expanding neutral vapor column. From these measurements we obtained the refractive index of the exploding wire vapor/plasma and used these results to find values for the plasma electron and neutral vapor densities.