Design optimization of the Hybrid Shock Drive platform for low-adiabat cryogenic implosions on OMEGA-60 and NIF

New designs for mitigating laser imprinting using an indirect-direct drive scheme [hybrid shock drive (HSD)] have been developed as a platform for low-adiabat spherical and polar cryogenic [inertial confinement fusion (ICF)] implosions at the Omega Laser Facility and the National Ignition Facility (NIF). Typical direct driven targets lack a buffer plasma between the ablator and the laser at early times, allowing speckles on the laser beams imprint high-ℓ-mode surface perturbations. This limits the minimum adiabat for stable implosions. The HSD designs described in this talk can enable lower adiabat, higher convergence and higher gain implosions for direct drive ICF and inertial fusion energy (IFE) applications. Simulations using the 2D radiation-hydrodynamics code DRACO, and experiments on the 60-beam OMEGA and OMEGA EP indicate that the HSD platform is capable of delivering a smooth x-ray shock and mitigating laser imprint in the ablator. Analysis of our experiments is guiding us to further improve our predictions. We will discuss the recent improvements in the HSD approach in order to obtain the maximum degree of implosion uniformity at all times. We will also discuss our next experimental steps on OMEGA-60 in our path to develop a cryogenic target for both OMEGA and NIF.