THE DEVELOPMENT AND ADVANTAGES OF BERYLLIUM CAPSULES FOR THE NATIONALIGNITION FACILITY

Capsules with beryllium ablators have long been considered as alternat ives to plastic for the National Ignition Facility laser [J. A. Paisne r et al., Laser Focus World 30, 75 (1994)]; now the superior performan ce of beryllium is becoming well substantiated. Beryllium capsules hav e the advantages of high density, low opacity, high tensile strength, and high thermal conductivity. Three-dimensional (3-D) calculations wi th the HYDRA code [NTIS Document No. DE-96004569 (M. M. Marinak et al. in UCRL-LR-105821-95-3)] confirm two-dimensional (2-D) LASNEX [G. B. Zimmerman and W. L. Kruer, Comments Plasmas Phys. Controlled Thermonuc l. Fusion 2, 51 (1975)] results that particular beryllium capsule desi gns are several times less sensitive than the CH point design to insta bility growth from deuterium-tritium (DT) ice roughness. These capsule designs contain more ablator mass and leave some beryllium unablated at ignition. By adjusting the level of copper dopant, the unablated ma ss can increase or decrease, with a corresponding decrease or increase in sensitivity to perturbations. A plastic capsule with the same abla tor mass as the beryllium and leaving the same unablated mass also sho ws this reduced perturbation sensitivity. Beryllium's low opacity perm its the creation of 250 eV capsule designs. Its high tensile strength allows it to contain DT fuel at room temperature. Its high thermal con ductivity simplifies cryogenic fielding. (C) 1998 American Institute o f Physics.