Cryogenic D-T fuel layers formed in 1 mm spheres by beta-layering

Solid D-T fuel smoothly layered on the interior of spherical capsules is re quired for all inertial confinement fusion ignition target designs. One pro cess for forming these layers, beta-layering, has been studied in surrogate geometries such as open cylinders or tori to allow accurate characterizati on of the DT surfaces. We present the first results from beta layering in 1 mm spherical containers, such as will be used in upcoming Omega experiment s. These results are also directly relevant to ignition capsules for the Na tional Ignition Facility. We find that layers can form with roughness as sm all as 1.2 microns rms, and that results are strongly dependent upon freezi ng rate as well as layer thickness.