The effects of laser absorption and mix on direct-drive capsule experiments at OMEGA

The yield of an ICF capsule can be affected by the inclusion of high-Z material in the fuel, either as a diagnostic or from hydrodynamic mixing. A series of experiments have been fielded at the OMEGA laser to better understand these effects. The targets are glass shells filled with a mixture of D$_{2}$ and $^{3}$He, and with controlled amounts of a dopant, Ar, Kr, and/or Xe. These targets are then directly driven with a 1.0 ns (0.6 ns) square laser pulse having a total energy of 23 kJ (13.8 kJ), and the data compared with yield and burn-temperature predictions from 1-d radiation-hydrodynamics calculations. However, our calculated yields are typically a factor of two greater than the measured yield, while the calculated burn-weighted temperatures are lower. Estimates for the amount of absorbed laser energy indicate that only 65{\%} to 70{\%} is absorbed. However, our calculations absorb 85{\%} of the energy. The ratio of D$^{3}$He-protons to DT-neutrons also indicates that mixing of shell material has occurred. We will discuss the results of recent 1-d calculations where the incident energy and flux limiter have been varied to match the absorption data. We will also discuss the use of a mix-model to match the charged particle data. Supported by US DOE and LANS, LLC under contract DE-AC52-06NA25396. LA-UR-09-04488