Probing the origins of hohlraum wall losses in ICF

Indirect Inertial Confinement Fusion (ICF) experiments at the National Ignition Facility (NIF) convert laser to x-ray energy using gold or depleted uranium hohlraums the dynamics of which strongly impact capsule implosion symmetry and ultimately fusion performance. Laser power multipliers, equivalent to a ~10-20 % in laser energy, are routinely employed in simulations to match experimental observables, such as x-ray flux reported by the Dante calorimeter and fusion bang-time.



To investigate the origin of the multipliers an experiment has been designed to investigate the origin of energy loss to the Hohlraum wall by driving a Marshak wave through a 6um gold foil at conditions equivalent to those present in an ICF hohlraum. The arrival time of the Marshak wave, measured simultaneously by a soft x-ray streak camera and the upper-hemisphere Dante soft x-ray power diagnostic, is used to constrain the product of multipliers on both the heat capacity and opacity; foil drive conditions are monitored throughout the experiment by the lower Dante. With sufficient constraint on the foil thickness, burnthrough time and x-ray drive we show that wall-losses can be constrainted to < 5%.



This work was supported by the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, supported by DOE Fusion Energy Sciences user FWP100182.