Pulsed power accelerators compress electrical energy in space and time to provide versatile experimental platforms for high energy density and inertial confinement fusion science. The 80-TW “Z” pulsed power facility at Sandia National Laboratories is the largest pulsed power device in the world today. Z discharges up to 22 MJ of energy stored in its capacitor banks into a current pulse that rises in 100 ns and peaks at a current as high as 30 MA in low-inductance cylindrical targets. Considerable progress has been made over the past 15 years in the use of pulsed power as a precision scientific tool. This paper reviews developments at Sandia in inertial confinement fusion, dynamic materials science, x-ray radiation science, and pulsed power engineering, with an emphasis on progress since a previous review of research on Z in Physics of Plasmas in 2005.
A coupled plasma sheath/ablation model is developed for electrothermal chemical gun applications. By combining a commonly employed collisional sheath model with a previous ablation model, the convective heat flux as a function of time to the propellant bed is determined for two potential electrothermal chemical gun propellants, XM39 and JA2. It is found that the convective heat flux varies smoothly from a nearly collisionless to a fully collisional regime over the short duration of the plasma pulse. The possibility of determining an accurate estimate of the amount of heat flux to the propellant bed due to radiation from the bulk plasma presents itself.
A computational fluid dynamics simulation of an expanding capillary plasma jet for electrothermal chemical (ETC) gun application is presented. A chemical model is developed for the plasma-air interaction that uses 26 species and 60 reactions in an implicit CFD code. Time accurate results are obtained for two plasma jet experiments, one with wall impingement with pressure sensor data from multiple locations, and another that decelerated the plasma through a plasma holding chamber, which greatly effected the chemical species present. Conclusions are drawn from the results that speak to the importance of the plasma-air interaction in actual ETC implementation. This work is part of a complete beginning-to-end model of the plasma propellant interaction currently being developed. Nomenclature T Temperature in Kelvin T e Electron temperature in eV u Flow speed in m/s ρ Mass density in kg/m 3 n Number density in m −3 P Pressure in Pa, ρRT P atm Pressure in atmospheres, P/(101325 Pa) X m Mole fraction of species m M Mach number, u/ 1.4P/ρ
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