Modeling NIF hohlraum experiments using wall opacity multipliers instead of laser power multipliers

Hohlraum experiments on the National Ignition Facility have shown measured x-ray drives consistently lower than predicted by simulations. This deficit has traditionally been addressed by artificially reducing the laser power incident to the hohlraum in the simulation by 10% or more. This modeling approach can be successful at matching observed implosion shock timing and bang times but invokes a decrement in the delivered laser energy many times the experimental uncertainty and also sacrifices accuracy in modeling the hohlraum plasma conditions. Here the prospects for matching observed hohlraum performance using a decrement in the hohlraum wall emissivity and/or an increment in the hohlraum wall specific heat, but no laser power multipliers, is explored for recent NIF experiments. Combined variations in the wall emissivity and specific heat not far outside of the expected 10% uncertainty are found to be sufficient to approximately match experimental shock timing measurements and bang times.