Improving Implosion Velocity in Cryogenic Deuterium--Tritium Implosions on OMEGA

This talk will summarize the results on improving performance and the progress in theoretical understanding of cryogenic deuterium--tritium implosions on OMEGA. To increase the implosion velocity, cryogenic layer thickness was reduced over the last year from 65 $\mu$m (which corresponds to $V_{imp} \sim $ 2.7 $\times $ 10$^{7}$ cm/s) down to 40 $\mu$m ($V_{imp} \sim $ 3.1 to 3.5 $\times $ 10$^{7}$ cm/s, depending on ablator thickness). The ablator thickness was varied from 9.2 to 13 $\mu$m. The shell is driven keeping fuel adiabat at $\alpha$ = 1.5 to 3. The experiments have demonstrated that the target yield relative to the 1-D predictions has not changed when the ice thickness is reduced to 55 $\mu$m ($V_{imp} \sim $ 3 $\times $ 10$^{7}$ cm/s), but degradation occurs for thinner ice. This degradation is more pronounced for designs with thicker ablator layers, indicating an enhanced ablator--pusher mix for these designs. Mix-mitigation strategies including high-$Z$ dopants in the ablator materials will be discussed. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302.