Robust MJ-class implosions at NIF: a framework and metrics for understanding ICF variability

Inertial confinement fusion (ICF) experiments at the National Ignition Facility (NIF) have culminated in a milestone experiment producing greater than 1 MJ of yield. The next at NIF is to develop implosions that robustly deliver this kind of MJ-class performance so that it can be harnessed routinely for a range of science and security experiments. We are developing new design and analysis tools to help us quantify the robustness of an implosion. We will report on two major thrusts. Thrust one focuses on efforts to quantify variability of existing implosion platforms. The goal is to deliver quantitative confidence limits on floors of neutron yield based on combinations of modeling and experimental observation. The second thrust focuses on developing design improvement paths that increase robustness (reduced variability). We will discuss versions of a new robustness metric that complements traditional ignition threshold metrics. This robustness metric aims to use observed stagnation conditions on a single shot to help infer the likely sensitivity of the implosion to uncontrolled sources of variation. We will discuss tools drawn from simulation, experiment, and AI-driven ensemble methods that enable these types of variability quantification and robustness estimation for the first time.