Hydrodynamic instabilities are known to limit ICF neutron production [ Haaetal]. For predictions of neutron production, the atomic level description of temperature and mixture concentrations provide the main input to a TN burn computation of neutron production [ CauFow88]. The interest in mix can be seen from the degradation of 40-75\% in neutron production, estimated [ WilEbeSann11]. based on experiments conducted on the Omega laser compared to the required maximum level of mixed fuel, estimated as 25\% to 40\% [ Haaetal]. Modal growth factors of 10 to 100 or more are reported in the linearized analysis of [ Haaetal], suggesting a role for the nonlinear turbulent mixing regime, beyond the ablation stabilized weakly nonlinear theory reviewed in [ LinAmeBer04].

Here we address validation/verification aspects of a hydro instability study related to these broad ICF concerns. Hydrodynamic mix has been identified as a possible cause of discrepancies between the design simulations and NIF experiments. There are three primary occasions during an ICF implosion in which mix plays a role. The first is the ablation instabilities at the outer edge of the capsule. It is known that simulations do not capture the extent of the ablation instability, which is a type of modified Rayleigh-Taylor instability. Next, there are a series of Rightmyer-Meshkov instabilities associated with the shock passage through the various layers of the ccapsule. Finally, at a late stage in the capsule implostion, and leading to the hot spot formation, there is a deceleration phase, which is Rayleigh-Taylor unstable. We study these instabilities and their relation to atomic scale mix.

The main thrust of the research proposed here is a series of A-B comparisons involving variation of codes (our front tracking code FronTier, the U. Chicago code Flash with and without front tracking and the LLNL code hydra and variation of other solution parameters which govern the extent of mix.