Surface roughness statistics and temperature step stress effects for D-T solid layers equilibrated inside a 2 mm beryllium torus

Abstract

Solid D-T layers are equilibrated inside a 2 mm diameter beryllium toroidal cell at temperatures ranging from 19.0 K to 19.6 K, using the beta-layering process. The experimental runs consists of multiple cycles of rapid- or slow-freezing of the initially liquid D-T charge, followed by a lengthy period of beta-layering equilibration, terminated by melting the layer. The temperature was changed in discrete steps at the end of some equilibration cycles in an attempt to simulate actual ICF target conditions. High-precision images of the D-T solid-vapor interface were analyzed to yield the surface roughness {sigma}{sub mns} as a sum of modal contributions. Results show an overage {sigma}{sub mns} of 1.3 {+-} 0.3 {micro}m for layers equilibrated at 19.0 K and show an inverse dependence of {sigma}{sub mns} on equilibration temperature up to 19.525 K. Inducing sudden temperature perturbations lowered {sigma}{sub mns} to 1.0 {+-} 0.05 {micro}m