Modelling high energy density systems with strong radiative loss using static mesh refinement

Radiative collapse occurs in dense plasmas where radiative loss drops the thermal pressure below the compressional magnetic pressure, leading to a runaway collapse to very small scale lengths. This is typically studied in Z-pinch plasmas when the current applied exceeds the Pease-Braginskii current (where the pinch is in pressure equilibrium). Studies have also been extended to X-pinch loads, where the crossing point between two wires forms a micro Z-pinch with even stronger j×B compression. The collapse can be terminated by various processes; development of instabilities, reaching the photon self-absorption (optically thick) limit, or in extreme cases the electron degeneracy limit.

Numerical modelling the evolution of radiative collapse up to termination is challenging because of the high resolution required to capture the final state. This work uses the newly implemented static mesh refinement (SMR) feature in the 3D extended-MHD code Gorgon to diagnose the final state of an X-pinch. SMR uses a series of nested grids of successively higher resolution placed in regions of interest, without requiring an expensive adaptive mesh refinement (AMR) treatment. Progress towards accessing and understanding this termination mechanism is presented and discussed.