Fusion Science and Technology / Volume 49 / Number 3 / April 2006 / Pages 500-516
Technical Paper / Fast Ignition
Fast ignition fusion targets require a uniform cryogenic D-T fuel layer for efficient fuel assembly. Uniform beta layering of solid D-T fuel within a fast ignition capsule will be complicated by the presence of a reentrant cone for short-pulse laser access. We discuss an alternative approach to cryogenic fast ignition targets currently being developed at Sandia National Laboratories in which a liquid cryogenic fuel layer is condensed from a low-pressure external gas supply and confined between concentric plastic shells. This concentric-shell cryogenic liquid fuel target concept is particularly well adapted to a hemispherical capsule configuration for single-sided X-ray drive. Liquid cryogenic D-T targets have a number of potential advantages, including greatly reduced system cost, temperature control, fill time, and cryogenic handling requirements, compared to beta-layered D-T targets. The shape and surface quality of the liquid fuel layer is determined entirely by the bounding shells, opening the possibility for simplified fast ignition fusion energy targets. Technology issues for target fabrication are discussed, and radiation-hydrodynamics simulations of liquid fuel capsule performance are presented.