Key advancements towards eliminating the 'drive-deficit' in ICF hohlraum simulations*

The predicted implosion performance of deuterium-tritium fuel capsules in indirect-drive inertial confinement fusion experiments rely on precision calculations of the x-ray drive inside a laser-driven cavity "hohlraum". This in turn requires accurate simulations of the conversion of laser power into a spectrally dependent x-ray source and the subsequent x-ray absorption losses in the hohlraum wall. A set of experiments have revealed that the inaccuracy in the emission calculation for the gold "M-band" is likely responsible for much, if not all, of the long-standing "drive-deficit" problem in ignition scale hohlraum simulations. These experiments were performed on ViewFactor targets with the gas fill and laser pulse shapes used in on-going ignition experiments on NIF. The common hohlraum model with MHD and a ~20% reduction to the "M-band" opacity can bring the simulations into agreement with two independent measurements: the absolute radiation flux (both total and "M-band") and spectroscopic measurements of K-shell dopants placed in the wall. Such a model is applicable to high-energy density experiments that use high-Z hohlraums as drivers.