Inertial confinement fusion (ICF) requires high compression of fusion fuel to densities approaching 1000 times liquid density of deuterium-tritium (DT), at central temperatures in excess of 5 keV. The direct-drive approach to ICF is more energy efficient than indirect drive if the stringent drive symmetry and hydrodynamic stability requirements can be met by a suitable laser irradiation and target design. Experiments using cryogenic fuel capsules in conjunction with distributed phase plates (DPPs) on the frequency-tripled OMEGA laser system have achieved compressed DT fuel densities in the 100-200 times liquid density regime, but the experiments exhibited deviations from one-dimensional performance. The deviations are believed to result from nonuniform implosion of fuel and shell material due to irradiation nonuniformities not removed by the DPPs. Improvements in irradiation uniformity through the use of a new technique, smoothing by spectral dispersion (SSD), may lead to reduced hydrodynamic instability growth and nearly one-dimensional capsule performance. SSD allows high-efficiency frequency tripling in a solid-state laser system.
Direct-drive inertial confinement fusion research at the Laboratory for Laser Energetics: charting the path to thermonuclear ignition