Thermal transport modeling of ICF Hohlraums and laser-irradiated spheres*

Radiation hydrodynamics simulations of ICF hohlraums commonly use a Spitzer-Harm thermal diffusion model that relies on an ad-hoc flux-limiter and fails to include pre-heat that would be driven by steep temperature gradients present in laser-heated targets. In this study, we examine the effects of improved electron heat transport modeling by comparing flux-limited diffusion models with an improved implementation[1] of the SNB[2] model in HYDRA. The impact of recent physics and algorithmic improvements to the nonlocal thermal transport models is quantified by performing simulations of ICF hohlraums (2D NIF Au-hohlraum post-shot models). We find that differences in modeled temperatures may be significant enough to cause variations in drive symmetry. The overall radiation drive, however, appears less sensitive to thermal conduction modeling than other physics models (e.g. NLTE kinetics in Au wall). In order to focus on the thermal transport, we also study laser illuminated spherical targets composed of lower-Z materials (e.g. Be, Al) in which non-LTE kinetics uncertainties are smaller and therefore less impactful on observables.

[1] Brodrick et. al, Phys. Plasmas 24, 092309 (2017)
[2] Schurtz et. al, Phys. Plasmas 7, 4238 (2000)