Conduction Solvers for Hohlraum Simulations

In indirect drive inertial confinement fusion (ICF) configurations, lasers deposit energy into hohlraum walls, which convert laser energy into the X-rays which, in turn, drive capsule implosions. The deposition occurs in a very thin region, leading to steep temperature and density gradients. Numerical solvers in xRAGE used to solve the nonlinear thermal conduction equations require special considerations to converge properly, such as using an accelerated fixed-point iteration to account for the large difference in conductivities and heat capacities between timesteps (B. M. Haines, et al. Physics of Plasmas. 2022). We explore the implementation of a new, adaptive accelerated pseudo-transient (APT) method and its impact on the performance and physics of hohlraum simulations. The APT method exhibits accelerated convergence in pseudo-time due to the use of a relaxed, Maxwellian flux in the derivation of the thermal conduction equations (L. Rass, et al. Geoscientific Model Development. 2022). We detail the new adaptive mesh implementation for xRAGE, compare against other solvers, apply these findings to mock hohlraum problems to study performance, and apply them to fully integrated hohlraum/target simulations.