Smoothing of deuterium-tritium ice by electrical heating of the saturated vapor

Abstract

High gain targets for inertial confinement fusion (ICF) are spherical shells which contain a layer of deuterium-tritium (DT) ice which surrounds a volume of DT gas in thermal equilibrium with the solid. The roughness of the inner surface of the cryogenic fuel layer inside of these targets is one of the sources of imperfections which cause implosions to deviate from perfect one-dimensional performance. Reductions in the surface roughness of this fuel layer improve confidence in the ability of the ICF program to achieve ignition in the National Ignition Facility (NIF), and increase the relevance of cryogenic experiments on the omega laser. We have developed a technique to generate a heat flux across this surface by applying an electric field to the DT vapor in the center of these shells. This vapor has a small but significant conductivity due to ionization caused by {beta} decay of tritium in the vapor and the solid. We describe here experiments using a 1.15 GHz cavity to apply an electric field to frozen DT inside of a sapphire test cell. The cell and cavity geometry allows visual observation of the frozen layers. We find that the resulting heat flux reduces the roughness of the icemore » surface. {copyright} {ital 1997} {ital The American Physical Society}« less