Visualizing hydrodynamic mix at capsule stagnation using spectroscopic marker layers in ICF implosions on the NIF

Hydrodynamic instabilities in ICF implosions can cause ablator material mixing into the hot spot plasma and shell rho-r variations which adversely impact the hot spot assembly and subsequent nuclear performance. To better understand this process in indirectly driven capsule implosions at the NIF, we have added a thin Ge dopant layer at the gas-ablator and ice-ablator interface in a series of non-DT layered symmetry capsule (Symcap) and DT layered implosions. This provides a spectroscopic marker for visualizing hydrodynamic mix during capsule stagnation. Comparison of the high-resolution, spectrally filtered Symcap hot spot images with those from `standard candle' Symcap implosions that do not have a Ge dopant allows us to measure how far ablator material is mixed into the hot spot. Complementary x-ray spectroscopy measurements constrain the thermodynamic state of the mixed ablator material. While the Symcap experiment shows enhanced x-ray emission from both the tent and fill-tube locations, the subsequent Ge- and Si-doped layered DT experiments show enhanced x-ray emission dominated by the fill-tube perturbation.

This work performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344.