Yield and compression trends and reproducibility at NIF

The yield and fuel compression trends for the NIF indirect-drive cryogenically-layered DT implosions is empirically examined across all ablators (CH, C and Be) and design in-flight adiabats between 1.5 and 3. Higher compression is observed for a lower design adiabat. Within a design adiabat, compression increases for shorter coast implosions but only if have optimized shock timing. The sensitivity of compression to coast time appears less for higher adiabat designs. Across all designs and ablators, the best DT neutron yields follow the same 1D theoretical curve versus peak velocity, but only if normalize by capsule scale rather than fuel mass and thickness. Shots with reduced yields can be explained by having long coast time, high hot spot mix or know capsule imperfections. Repeat “Standard Candle” shock timing and gas implosions, and DT layered implosions normalized for scale and velocity, reveal adequate reproducibility in shock timing, implosion drive symmetry, compression and yield for the majority of shots. The level of reproducibility is also consistent with known uncertainties and imperfections in initial laser and capsule parameters and outputs. We thus conclude there is no evidence of a significant random unknown variable in these NIF implosions. The scaled yield reproducibility is such that the effect of design improvements increasing yield on any given shot by at least 40% can be deemed statistically significant.