Plasma hydrodynamic experiments on NRL Nike KrF laser

Abstract The krypton-fluoride Nike laser delivers up to 2 KJ in 248 nm ultraviolet radiation to planar targets with the most uniform illumination of all existing high-energy lasers for inertial confinement fusion (ICF) research. That, combined with high-resolution monochromatic x-ray imaging pioneered at NRL in the 1990s and the recently added two-dimensional (2D) VISAR diagnostics, provides a unique platform for experimental studies of hydrodynamic phenomena important to the inertial confinement fusion (ICF). These include absolute experimental determination of the primary Hugoniots of low-density plastic foams in the Mbar pressure range. Although foam materials have many uses for the manufacturing of ICF targets ranging from laser fusion to Z-pinch-driven dynamic hohlraums, no experimental data on their shock compressibility in the ICF-relevant pressure range was available until our experiments. We describe the first systematic experimental study of the nonlinear, multi-mode perturbation evolution triggered by localized target non-uniformities, such as straight grooves and dots, which emulate fill tubes, tents, and other target-mounting structures in laser capsules. The experimental data turned out to be counter-intuitive and challenging for simulations. Finally, the 2D VISAR snap-shot images of the shock velocity field made it possible to directly measure the roughness of a uniformly driven shock front propagating into the target, which is caused by ISI-smoothed laser imprint. Initial measurements for planar CH targets with and without thin high-Z layers added for the imprint mitigation have been successfully performed.