Study of the emissivity of the rear face of a shocked foil with temporal and X-UV spectral resolution in single and colliding foil experiments

Abstract

The emissivity of the rear of a shocked foil is spectrally and temporally resolved by coupling a transmission grating (1000 I/mm) and an X-UV streak camera (with a low density Csl photocathode), providing a high temporal resolution over a large spectral range. The shock is generated with two techniques: direct illumination of a single Al foil with a 0.26 μm wavelength laser (ablation pressure ≈ 50 Mbars) or by colliding an Al foil with a laser accelerated CH foil (generated pressures greater than 100–200 Mbars). Different thicknesses of Al are used in single foil experiments, and different initial spacing and impacted foil thicknesses are used in double foil experiments. Double foil experiments indicate that targets can be optimized for high pressure generation, and single foil experiments show that there is a radiative heat wave, around 200 eV, due to the heating of the foil by X rays emitted in the ablated region during the laser pulse. Double foil experiments have been compared with 2-D hydrodynamic Lagrangian simulations and single foil experiments have been compared with 1-D hydrodynamic Lagrangian simulations taking into account radiative heat transfer.