Extended MHD simulations of FRC formation, translation, and capture in stationary and imploding liners

Abstract

Summary form only given. The U.S. Air Force Research Laboratory Directed Energy Directorate and Los Alamos National Laboratory are forming, translating, capturing, and compressing magnetic field-reversed configuration plasmas (FRCs) in stationary and imploding aluminum cylinders, with the goal of creating a high-energy-density magnetized plasma configuration. We have previously described 1 2-d axisymmetric magnetohydrodynamic (MHD) simulations of these experiments with the geometric configuration of the actual device driven by the time-dependent currents of its pulsed power systems. Our simulations begin with the theta-pinch preionization phase based on the experimentally determined breakdown/ionization time to produce the correct flux trapped in the FRC and thus improve agreement with the experimental magnetic probe data. They have become the theoretical workhorse for delivering understanding of those experiments and assessing the potential impact of design variations upon them. FRC experiments have shown evidence of plasma rotation, a process which can lead to amplification of asymmetry and subsequent collision of plasma with the wall. In cylindrical symmetry, the magnetic force from either poloidal field or toroidal field alone has no toroidal component, but when all three components of the field are present, toroidal force and hence rotational acceleration are possible. Furthermore, in the presence of toroidal current, the Hall Effect can shear radial field into the toroidal direction, converting some poloidal field into toroidal field. Hence, extended MHD (XMHD) is necessary in order to model the generation of rotation in axisymmetric simulations of plasma motions induced by toroidal coils only.