Extension of the Spk Atomic Physics Code to Generate Global Equation of State Data

Global microphysics models are required for the modelling ofhigh-energy-density physics (HEDP) experiments, the improvement of which arecritical to the path to inertial fusion energy. This work presents furtherdevelopments to the atomic and microphysics code, SpK, part of the numericalmodelling suite of Imperial College London and First Light Fusion. We extendthe capabilities of SpK to allow the calculation of the equation of state(EoS). The detailed configuration accounting calculations are interpolated intofinite-temperature Thomas-Fermi calculations at high coupling to form theelectronic component of the model. The Cowan model provides the ioniccontribution, modified to approximate the physics of diatomic moleculardissociation. By utilising bonding corrections and performing a Maxwellconstruction, SpK captures the EoS from states ranging from the zero-pressuresolid, through the liquid-vapour coexistence region and into plasma states.This global approach offers the benefit of capturing electronic shell structureover large regions of parameter space, building highly-resolved tables inminutes on a simple desktop. We present shock Hugoniot and off-Hugoniotcalculations for a number of materials, comparing SpK to other models andexperimental data. We also apply EoS and opacity data generated by SpK inintegrated simulations of indirectly-driven capsule implosions, highlightingphysical sensitivities to the choice of EoS models.