A physics-based simulation framework for resolving ignition-scale hohlraum drive discrepancies

Simulations of laser-indirect drive hohlraums routinely predict that the peak capsule neutron production time occurs 400–600 ps earlier than measured and overpredict the amount of x-ray production in the hohlraum. Here, several modeling improvements are shown to largely eliminate this discrepancy. Where possible, these modeling choices are constrained by measurement. A set of opacity multipliers on the wall materials and the ablator are also introduced. Expressions constraining multipliers on the equation-of-state of the wall materials are also introduced in order to agree with previous experiments reported in the literature. An optimization is then performed by comparison of simulations of a suite of experimental results to determine the values of these multipliers. The resulting model agrees with bangtime measurements within 150 ps for 12 of 14 shots simulated and within x-ray drive measurement uncertainty for a majority of the shots in the suite. The model is then applied to a recent set of ViewFactor experiments, which measured both x-ray drive and inferred plasma conditions through x-ray spectroscopy. This model is shown to be consistent with the set of measurements. Thus, an improved approach that statistically removes the drive discrepancy is shown. This approach is unable to match implosion symmetry measurements and has not been validated at scales beyond those of current ignition experiments at the National Ignition Facility.