Simulating radiatively driven magnetized shock experiments using a variable Eddington factor radiation model

Experiments studying radiatively driven magnetized shocks [1] have been carried out at Imperial College London. Two planar silicon targets are ablated by X-rays produced by a wire array Z-pinch. This produces two counter-propagating magnetized plasma flows that collide, forming radiative shocks. The colliding flows have a quasi-2D geometry allowing for well-defined experimental data compared to more complex schemes typical of HEDP. In this work, we simulate these experiments using a radiation transport and MHD code Chimera [3] in order to investigate the sensitivity of the simulations to how radiation transport is modelled. The radiation moment equations are obtained by taking successive angular moments of the radiation transport equation. An additional expression for the radiation pressure tensor is required to close the system of equations. The P1/3 closure assumes a scalar radiation pressure while the variable Eddington factor (VEF) closure assumes the radiation pressure tensor is an analytic function of the local radiation energy density and flux [4]. The VEF closure is better suited to anisotropic radiation fields than its P1/3 counterpart as it retains some of the angular structure. Regions of the silicon targets facing the Z-pinch experience a higher intensity of incident radiation and are therefore preferentially ablated. Initial results indicate an anisotropic treatment of the radiation transport such as a VEF closure is required to capture the subsequent non-uniform ablation of the target.