A Thin Feedthrough Richtmyer-Meshkov Experiment at the NIF

The Richtmyer-Meshkov instability (RMI) arises when a shock crosses the boundary between materials of disparate densities. In an ICF capsule, the boundary between the thin ablator layer and cold fuel can give rise to the RMI. RMI leads to large bubbles and spikes, causing mixing between the ablator and fuel, reducing performance. Secondary shocks from the source, as well as rarefactions and reflections within the capsule can drive the RMI into a turbulent state, further degrading the performance. The Mshock platform is studying the RMI in a thin layer similar to an ICF capsule, but in a planar geometry. The goals are to understand how the instability is affected not only by initial conditions, but how it responds to being shocked multiple times. Recent experiments at NIF have tested the feedthrough of two initial conditions with a similar single mode perturbation, but a different broadband profile with a shock and re-shock setup. The results indicate that the mixing is highly dependent on the initial condition. Detailed analysis and comparison with LANL’s BHR mix model are currently underway. This talk will discuss the platform and experimental results, and give a preliminary comparison with the BHR mix model.