Cryogenic target-implosion experiments on OMEGA

The University of Rochester's Laboratory for Laser Energetics has been imploding thick cryogenic targets for six years. Improvements in the Cryogenic Target Handling System and the ability to accurately design laser pulse shapes that properly time shocks and minimize electron preheat, produced high fuel areal densities in deuterium cryogenic targets (202±7 mg/cm2). The areal density was inferred from the energy loss of secondary protons in the fuel (D2) shell. Targets were driven on a low final adiabat (α = 2) employing techniques to radially grade the adiabat (the highest adiabat at the ablation surface). The ice layer meets the target-design toughness specification for DT ice of 1-μm rms (all modes), while D2 ice layers average 3.0-μm-rms roughness. The implosion experiments and the improvements in the quality and understanding of cryogenic targets are presented.