Multi-physics simulations of ICF capsules using high-order finite-element discretizations*

High-order numerical discretizations provide increased accuracy per degree of freedom and higher FLOP/byte compute ratios when compared against standard lower-order approaches. This work focuses on simulations of ICF capsules using the higher-order finite-element multi-physics code Marbl. Whereas traditional lower-order codes use linear functions to represent the kinematic variables and piecewise-constant fields for the thermodynamic variables, Marbl relies on quadratic polynomials for the kinematic variables and linear functions for the thermodynamic variables. We report on simulations of two ICF capsule implosions, namely those corresponding to the igniting NIF shots N210808 and N240212. Differences between high- and low-order results are analyzed. The capsule simulations exercise various physics packages, including multigroup radiation transport, ion and electron thermal conduction, and thermonuclear burn. We provide details on our approach to ALE relaxation, time-step restrictions, mesh smoothing, and solver tolerances, etc. that were required to achieve stable and accurate simulations in one, two, and three dimensions when using the high-order discretizations.