Proposed Code Validation of Convergent Shock Interactions*

Simulation in 2D radiation hydrodynamic codes of experimental convergent geometries, such as those found in hohlraum simulations, inertial confinement fusion, or converging, cylindrical experiments (Sauppe, J. P. et al, Phys. Plasmas 26, 042701 (2019); doi: 10.101063/1.5083851) can lead to the prediction of on-axis features that may not be experimentally present.  Of concern is the numerical nature of physics models and their interactions near the axis of symmetry where computational, numerical noise can impact the calculations occurring in the simulations.  We propose a possible experimental platform that could be fielded at the National Ignition Facility that can measure the formation of an on-axis feature with sufficient resolution that it could be compared to simulation and used to validate the predicted on-axis shock interaction in a cylindrically convergent geometry.  We will show that the radiation from a hohlraum can be used to create a cylindrically converging shock and that experimental measurements can be taken to characterize the uniformity of the converging shock and the resultant interaction.  Such measurements can be used to validate a simulation approach that accurately captures the results of an on-axis, convergent-shock interaction.