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Summary form only given. Experiments on the National Ignition Facility (NIF) have employed the first four beams to measure propagation and laser backscattering losses in large ignition-size plasmas. Gas-filled targets between 2 mm and 7 mm length have been heated from one side by overlapping the focal spots of the four beams from one quad operated at 351 nm with a total intensity of 2times1015 W cm-2. The targets were filled with 1 atm of CO2 producing of up to 7 mm long homogeneously heated plasmas with densities of ne = 5times1020 cm-3 and temperatures of Te = 2 keV. The high energy in a NIF quad of beams of 16 kJ, illuminating the target from one direction, creates unique conditions for the study of laser plasma interactions at scale lengths not previously accessible. The propagation through the large-scale plasma was measured with a gated X-ray imager that was filtered for 3.5 keV X-rays. These data indicate that the beams interact with the full length of this ignition-scale plasma during the last ~1 ns of the experiment when applying full laser beam smoothing consisting of phase plates, smoothing by spectral dispersion and polarization smoothing. Measurements that only apply phase plates show, laser beam filamentation and reduced propagation speed. These results demonstrate the NIF experimental capabilities and further provide a benchmark for three-dimensional modeling of the laser-plasma interactions at ignition-size scale lengths

Summary form only given. Indirect drive performance for inertial confinement fusion depends to a large degree on the ability to mitigate wall losses in the hohlraum. One approach to do this is based on the use of hohlraum wall materials with overlapping absorption bands to absorb and re-emit the radiation that otherwise would be lost. Albedos for various combinations of these materials, so-called cocktails, have been calculated and a mixture of U, Dy and Au has been determined to be the best candidate. However, these calculations are based on published values of heat capacity and opacity and do not take into account possible material oxidation. In order to obtain accurate material data and to test the influence of oxygen two experimental campaigns were designed for the Omega laser facility in Rochester. The first experiment uses a laser energy of 7 kJ to heat a halfraum to a radiation temperature of 250 eV. The backwall of the half hohlraum consists of a split foil arrangement of two different materials and the re-emission characteristics and the burn through time of the foils are measured using framing and streak cameras. Using foils of each material and a combination of both materials allows us to determine heat capacity and opacity for each material. The 2nd campaign uses 20 kJ of laser energy to drive Au and cocktail hohlraums. Cocktail materials with varying oxygen content are tested and the difference in soft X-ray drive is measured using a soft X-ray spectrometer (DANTE). Experimental results will be presented testing our understanding of high-Z cocktail radiation properties