An advanced model of a high pressure liquid dielectric switch for directed energy applications

A high power liquid dielectric switch is being developed to satisfy the requirements for future directed energy applications. A flowing, high-pressure liquid dielectric was chosen for the design of a megavolt class switch operating at 100 pps. This paper reports on the modeling efforts commensurate with the design of a full size, prototype 250-300 kV concept validation test (CVT), switch that can transfer kilojoules per pulse. The flow system required to clear the discharge bubble and byproducts is intimately tied to the dynamics of energy deposition, and bubble formation. A circuit model has been developed to predict the discharge temporal characteristics including the voltage, current, risetime, arc energy deposition profile, and time varying arc inductance, bubble formation timescales and oscillatory bubble effects. The model utilizes both the Braginskii equation and Charlie Martin's equations to calculate the energy dissipated in the arc. A comparison of the two methods is presented. An integrated model also includes the hydrodynamic equations to predict the gas bubble volume and oscillation period, which are dramatically reduced with increasing pressure. Optimization studies indicate that a 1000-2000 psi switch appears to have ideal attributes including minimal dielectric flow requirements, compact size and low weight for implementation of a kilojoule, rep-rate switch.