Simulations of the 3-Shock HDC gas-filled hohlraum experiments at the NIF*

We describe simulation efforts to design and field a series of high-density-carbon [1] (HDC) capsule tuning experiments in 1.6 mg/cc gas-filled hohlraums at the National Ignition Facility (NIF), culminating in two DT-layered shots. The radiation-hydrodynamics code HYDRA coupled to an off-line power transfer model was employed to ascertain the optimal laser pulse that minimizes radiation asymmetries and implosion adiabat for a given stability margin. We found that these HDC targets have similar sensitivity as their CH ``high-foot'' [2] counterparts when laser cone-fraction and power as well as ablator thickness are varied, leading to comparable implosions. A point of divergence, however, is the measured neutron down-scatter-ratio (DSR) that typically gauges the degree of compression obtained in a DT implosion, with HDC targets having approximately half the CH value. Concerted efforts are underway to understand and ascertain the causes of this discrepancy. Simulations and comparisons with data will be presented. \\[4pt] [1] D. Ho et al, BAPS.2012.DPP.GO4.13.\\[0pt] [2] O. Hurricane et al, Nature 506, 343 (2014).