Spherical Strong-Shock Inferences on OMEGA

A milestone for shock ignition\footnote{ R. Betti \textit{et al}., Phys. Rev. Lett. \textbf{98} 155001 (2007).} is to experimentally verify the generation of several hundred Mbar shocks at shock-ignition--relevant laser intensities. This paper presents the first experimental evidence of strong shocks generated in a spherical geometry. Using the temporal delay between the launch of the strong shock at the outer surface of the spherical target and the time when the shock converges at the center, the shock properties can be inferred using radiation--hydrodynamic simulations. Peak ablation pressures exceeding 200 Mbar are inferred at laser intensities of $\sim 3 \times 10^{15}$ W/cm$^2$. The shock strength is significantly enhanced by the coupling of copius amounts of hot electrons, up to 2 kJ with $T_{\mbox{hot}} \sim$ 50 to 100 keV. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and the Office of Fusion Energy Sciences Number DE-FG02-04ER54786.