First observations of distinct RM growth scenarios for successively shocked interfaces

Inertial Confinement Fusion (ICF) and High-Energy Density Physics (HEDP) experiments experience complicated forcing for instability growth and mix, due to the ubiquitous presence of multiple shocks interacting with perturbations on multiple material interfaces. One common driver of instability growth is successive shocks from the same direction. However, there is a severe lack of analytic work and modeling validation for same-sided successive shocks since they are extremely difficult to achieve with conventional (non-HED) drivers. Successive shocks access a large instability parameter space; idealized fluid theory [Mikaelian, PRA 31(1), 410 (1985)] predicts 15 different interface evolution scenarios for just a single mode. Growth becomes more complex for multi-mode, compressible HED systems. The Mshock campaign is the first experiment in any fluid regime to probe a wide portion of successive shock parameter space. This is enabled by our development of a hybrid direct/indirect drive capable of creating independently controllable successive shocks using a hybrid direct/indirect drive on the NIF. These experiments have delivered the first data capable of rigorously challenging our models and their ability to accurately capture Richtmyer-Meshkov growth under successive shocks.

Single-mode experiments have successfully demonstrated the ability to access and control the various growth states of the shocked interface, including re-inversion, freeze-out, and continued growth. Data is shown to agree between experiment, theory, and simulation in the linear growth phase, giving us confidence in our ICF/HED design codes. Multi-mode experiments demonstrate distinct growth scenarios for the different modes and form a first basis of tests for initialization parameters of non-linear instability and turbulence models [Braun and Gore, Physica D, 404 (2020)] in this regime.