Simulation of an exploding wire opening switch

Abstract

An exploding wire model that accounts for the electric field enhanced conductivity of dense metal plasma is applied to simulate an exploding wire opening switch. In contrast to many z-pinch experiments, operated in vacuum, the experiments here discuss wires vaporized in a high pressure gas environment. In addition to this, these experiments are primarily concerned with sub-eV temperatures, with a specific emphasis on the liquid-vapor phase transition, where significant decreases in conductivity provide the opening switch behavior. It is common that fuses operating within this regime are analyzed using 0-dimensional models, where the resistance is taken to be an experimentally determined function of energy or action. A more accurate 1-dimensional model with added field enhanced conductivity has been developed to better model the fuse dynamics throughout a significantly larger parameter range. The model applies the LANL SESAME database for the equation-of-state, and the conductivity data developed with the Lee-More-Desjarlais (LMD) algorithm. Using conductivity based on conditions of thermal equilibrium accurately predicts fuse opening as well as current re-emergence after a few microseconds dwell time for the case of small electric fields, however, this simple approach fails to capture early fuse restrike if the differential voltage across the wire becomes too large (~few kV/cm for the investigated conditions). It is demonstrated that adding an electric field driven conductivity term to the model will accurately capture the fuse dynamics for the low field as well as the high field case.