Density fluctuation measurements of HED thin-layer Richtmyer-Meshkov experiments

The applicability and implementation of turbulent mix models in the high-energy-density regime is a fundamental question for ICF as the impact of mix includes the quenching of ignition experiments by mixing hot fuel with cold external materials. LANL has developed an experimental suite on the NIF capable of studying RM growth and transition to turbulence in the ICF-relevant regime, with a fundamental focus to test the applicability and performance of the BHR mix model in this complex, HED regime. To constrain mix model performance, we built on previous work [Kurien et al. Physics D, 2020] to develop an analysis method to extract statistics of density fluctuations from radiographs, specifically the BHR density-specific-volume covariance, b = -<ρ′ (1/ρ)′>, where ρ is the density, ρ′ is the density fluctuation, and the fluctuations are ensemble averaged. We present results from the NIF thin-layer Mshock reshock experiment [T. R. Desjardins et al., HEDP 2019], demonstrating the ability to extract 1D profiles of b in addition to traditional mix width measurements. Comparisons show good agreement with simulations, and potentially a method for disambiguating EOS and mixing effects in our modeling.