Hierarchical Bayesian Modeling of Ablation Pressure in Laser-Driven Implosion Experiments

In laser-driven implosion experiments, high-intensity lasers are used to compress a capsule to high-energy-density (HED) conditions comparable to those found in star and planet interiors, enabling studies of astrophysical phenomena and inertial confinement fusion. The principal mechanism compressing the target is ablation, by which the laser-heated outer layers of the target are ejected at high velocity, exerting an inward pressure on the target interior. Previous theoretical and experimental work has shown that ablation pressure scales as a power law of the incident laser intensity, but direct measurements in implosion experiments are often challenging in convergent geometry. In this work, we analyze trajectory data from multiple x-ray self-emission diagnostics from an ensemble of implosion experiments of gas-filled plastic shells driven by various laser pulses on the OMEGA laser. The data are jointly analyzed in a hierarchical Bayesian framework to infer the scaling of ablation pressure up to peak laser intensities of 2 × 10¹⁵ W/cm². The results of this analysis enable quantitative testing of ablation physics models with full uncertainty quantification, providing essential insight into the dynamics of laser coupling efficiency.