A comparison of the electrodynamics of metals under the action of large electric currents

Abstract

A numerical investigation of the behavior of electrically thin exploding foils is presented. This work examines the effect that non-linear material properties have on the electrodynamic behavior of three metallic bridgefoils (Al, Cu, Au) having identical geometries but different material compositions. Previous experimental work and simulations focused on copper bridgefoils electrically excited using the first quarter cycle of a 1200 A, 1.7 Mhz current source. This high power current pulse induced solid to vapor phase transitions over the entire foil surface in exploding foil experiments. Use of a finite element code (FEM) to determine the transient thermal and electrical effects in the pre-melt regime has been previously demonstrated for copper. The FEM code solves two non-linear partial differential equations which account for the thermal conductivity, latent heat of fusion, and specific heat(C _{\rm v} ) of the foil. The focus of this research is to contrast the simulated behavior of three metal foils (Al, Cu, Au) by examining corresponding plots of electrical and thermal signatures as the foils progress temporally to melt. The model predicts that the pattern of pre-melt behavior for all three foils is similar. The time to melt was found to be shortest for gold, followed by copper, and finally, aluminum ( T_m {\rm Au}< T_m {\rm Cu} < T_m{\rm Al} ).