RESUMO
In this work, we present results from experiments capable of producing and measuring the propagation of multiple successive, copropagating shocks across an unstable planar interface, where the shocks are independently driven and separately controllable, enabling the study of this important phenomenon. Copropagating shocks play a significant role in a wide range of systems involving stratified media subject to a shock, and exhibit different physical characteristics compared to counterpropagating shocks. Existing techniques, however, preclude copropagating shocks, so experiments to date have been limited to the study of counterpropagating shocks. We address this previous limitation and open a physical parameter space for study using a new hohlraum platform on the National Ignition Facility. Initial experimental results are presented together with comparisons from numerical simulations.
RESUMO
In order to investigate the role of both neutral and ion dynamics in large-scale helicon discharges, a laser induced fluorescence (LIF) system capable of measuring both ArI and ArII fluorescence using a single tunable laser is being developed. The system is based on a >250 mW solid state laser. For ArI measurements, the laser pumps the metastable (2P03/2)4s level to the (2P01/2)4p level using 696.7352 nm light, and fluorescence radiation from decay to the (2P01/2)4s level at 772.6333 nm is observed. For ArII, currently in development, the metastable (3P)3d 4F7/2 level will be pumped to the (3P)4p 4D07/2 level using 688.8511 nm, and decay fluorescence to the (3P)4s 4P5/2 level at 434.9285 nm measured. Here all wavelengths are in a vacuum.