Influence of Cocktail Material Parameters on Indirect Drive Holhraum Performance

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 2^nd 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