Improving efficient electronic stopping power models with first-principles benchmarks*

Hydrodynamic simulations of fusion experiments rely on tabulated electronic stopping powers, which govern self-heating on the way to ignition. We use real-time time-dependent density functional theory (TDDFT) to benchmark and constrain efficient stopping models suitable for tabulation in the warm dense regime. First, we consider different treatments of electron-ion collisions in the Mermin dielectric formulation for the free-electron contribution to proton stopping powers and find that T-matrix or Kubo-Greenwood approaches improve agreement with TDDFT over the Born approximation [1]. Then, we examine deviations from Z² scaling between proton and alpha stopping powers predicted by TDDFT near and below the Bragg peak, and we evaluate effective charge models for capturing this behavior. Finally, we leverage recent methodological advances [2] to study the validity of additivity laws for mixtures. Throughout, we survey a range of warm dense systems, including hydrogen, deuterium, carbon, and aluminum. These efforts will enable more accurate stopping power models used to design and interpret fusion experiments.

1. Hentschel et al., Physics of Plasmas 30, 2023

2. Kononov et al., arXiv:2307.03213, 2023