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

TL;DR

This paper extends the SpK atomic physics code to generate comprehensive equation of state data, enabling detailed modeling of high-energy-density physics experiments and improving simulation accuracy for inertial fusion research.

Contribution

The authors develop and implement a new extension to the SpK code that calculates a global equation of state, integrating electronic and ionic contributions with advanced corrections.

Findings

SpK can now produce detailed EoS tables rapidly on a desktop.

The extended model accurately reproduces shock Hugoniot data for various materials.

Simulations using SpK EoS data show significant sensitivities in capsule implosion outcomes.

Abstract

Global microphysics models are required for the modelling of high-energy-density physics (HEDP) experiments, the improvement of which are critical to the path to inertial fusion energy. This work presents further developments to the atomic and microphysics code, SpK, part of the numerical modelling suite of Imperial College London and First Light Fusion. We extend the capabilities of SpK to allow the calculation of the equation of state (EoS). The detailed configuration accounting calculations are interpolated into finite-temperature Thomas-Fermi calculations at high coupling to form the electronic component of the model. The Cowan model provides the ionic contribution, modified to approximate the physics of diatomic molecular dissociation. By utilising bonding corrections and performing a Maxwell construction, SpK captures the EoS from states ranging from the zero-pressure solid, through the liquid-vapour coexistence region and into plasma states. This global approach offers the benefit of capturing electronic shell structure over large regions of parameter space, building highly-resolved tables in minutes on a simple desktop. We present shock Hugoniot and off-Hugoniot calculations for a number of materials, comparing SpK to other models and experimental data. We also apply EoS and opacity data generated by SpK in integrated simulations of indirectly-driven capsule implosions, highlighting physical sensitivities to the choice of EoS models.