SURFACE-ROUGHNESS MEASUREMENTS OF BETA-LAYERED SOLID DEUTERIUM-TRITIUM IN TOROIDAL GEOMETRIES

New experiments in a NIF-scale toroidal cylinder have resulted in true shadowgraphs of the DT ice surface. The spectral analysis of the imag es summed over l-modes 2 through 256 reveal that the surface roughness reaches values just below 1.0 mu m at temperatures of 19 K and above. Summing only modes l greater than or equal to 10, the partial surface roughness is below 0.7 mu m at 19.5 K. These results indicate that na tive beta-layering will be sufficient to meet the NIF requirements for DT ice surface finish for both Be and CH ablating shells. The toroida l cylinder incorporates a linear heater along the cylindrical axis to test the concept of surface enhancement due to heat assisted beta-laye ring in DT. Additionally, with the use of this heater it is possible t o symmetrize a pure D-2 layer.