Numerical Modeling of Plasma Formation with Megagauss Magnetic Fields

Summary form only given. Metal plasma formation and stability were studied on the surface of typical liner materials in a recent series of experiments driven by the UNR Zebra generator. The surface response to megagauss (MG) fields is important for a number of applications, including magnetized target fusion. Recent radiation-hydro numerical simulations in a planar geometry by Garanin et al. show how plasma can be generated through thermal processes on a metal surface. The surface response of aluminum cylindrical conductors was modeled numerically assuming experimentally relevant current rise-times, which determine the ratio of current skin depth relative to conductor radius. Important effects include plasma formation, radiation transport, and the unstable m=0 mode driven by curvature of the magnetic field that holds the surface plasma against the metal. Numerical simulations with codes used at UNR (MHRDR and RAVEN) show luminosity, radial expansion, and plasma formation that can be compared with experimental data. Interesting details such as a compression wave that propagates from the surface to the axis and back are more difficult to diagnose experimentally, but are possibly connected with the observation of surface expansion after the time of peak current. Results from other codes and the sensitivity of modeling to various equation-of-state and resistivity models are also discussed.