Light-to-heavy Richtmyer-Meshkov instability experiments on the NIF

We report initial results from a NIF Discovery Science campaign to study Richtmyer-Meshkov instability (RMI) growth when a strong shock transits from a low- to high-density interface - the canonical “light-to-heavy” configuration widely explored in gas-driven shock tubes but not previously on NIF. The target couples a high-energy laser drive to an ablator which shock-accelerates a foam-plastic interface seeded with separate 100 and 200 µm sinusoidal modes in an iodine-doped CH tracer. The physics package dimensions were selected to maximize singly-shocked growth while minimizing Rayleigh-Taylor stabilization. The first three shots acquired BABL backlit radiographs at 55-70 ns. Unexpectedly low backlighter fluence provided too-low SNR on the primary gated x-ray detector, yet time-integrated image plate data shows mode growth broadly consistent with design simulations. A second shot day fields a higher-gain gated x-ray detector with a switch from Zn to Ni backlighting to improve SNR, enabling quantitative wavelength-resolved growth extraction and comparison to legacy UW-Madison shock tube and Omega-EP light-to-heavy RMI data. The presentation will cover platform design, experimental data, and preliminary analysis including a comparison to HYDRA simulations.