High-Areal-Density Cryogenic D$_{2}$ Implosions on OMEGA

The validation of direct-drive ignition target designs on OMEGA requires the demonstration of both 1-D burn and 1-D areal density (\textit{$\rho $R}) up to the point of mix truncation with cryogenic fuel on an adiabat of $\le $4 and a peak implosion velocity of $\sim $3.5 $\times $ 10$^{7}$ cm/s. We report here on the demonstration of 1-D \textit{$\rho $R} in a series of cryogenic D$_{2}$ implosions with a fuel adiabat of $\sim $2. The targets consisted of a thick CD ablator (10-\textit{$\mu $}m wall) and a fuel layer of $\sim $95 \textit{$\mu $}m of D$_{2}$. The inner-surface roughness of the ice was $\sim $2-\textit{$\mu $}m rms. With an 18-kJ decaying shock drive pulse with a peak intensity of 5 $\times $ 10$^{14}$ W/cm$^{2}$, the $\langle $\textit{$\rho $R}$\rangle $ was 202 mg/cm$^{2}$ (95{\%} of 1-D). The thick CD ablator mitigates hot electron preheat from the two-plasmon-decay instability in hydrogen---by design, no hydrogen reaches the quarter-critical density surface. Future experiments will focus on areal density performance at higher implosion velocities. This work was supported by the U.S. DOE Office of ICF under Cooperative Agreement DE-FC52-92SF19460.