Equation of state and electron transport effects in exploding wire evolution

Summary form only given. The detailed evolution of each exploding wire comprising a cylindrical array determines the energy and power densities ultimately achievable in a z-pinch implosion of the array. Presumably, once the relationship between exploding wire evolution and z-pinch dynamics is understood sufficiently, one could design a z-pinch experiment that would produce the optimum behavior for a given application. Before attempting to team how exploding wire evolution affects z-pinch behavior it is crucial to be able to accurately model the single exploding wire. Toward that end we have been doing single-exploding-wire simulations in the z-r plane with the MHD code MACH2 and with Sandia´s new code ALEGRA. We have so far limited our study to the radial evolution. Our standard configuration corresponds to recent, well diagnosed exploding aluminum wire experiments from Cornell (Sinars et al., 2000). Simulations show that the path in phase space that an exploding wire takes in its evolution from solid metal to high-temperature plasma is quite sensitive to the EOS and conductivity models used. We have been guided by comparing the simulations with the Cornell data while maintaining as a constraint the consistency of our models with known EOS and conductivity data (DeSilva and Katsouros, 1998) from independent experiments and with modern physical descriptions appropriate in the parameter regime of the metal-insulator transition (Desjarlais, 2001). A novel view of exploding wires allows us to see graphically the mutual relations between the EOS and the electrical conductivity during the exploding wire´s evolution. A key feature that occurs under certain conditions, as observed in experiments, is the transition to a coronal state (most current flowing through the rapidly-expanding low-density ionized vapor at large radius); a rapid transition coincides with a voltage collapse. How wire current, dI/dt, wire material, wire diameter, initial density profile, and initial - ire temperature affect the wire evolution will also be discussed.