Direct-Drive--Ignition Designs with Moderate-\textit{Z} Ablators

Mitigation of laser--plasma and hydrodynamic instabilities is crucial for the ultimate goal of ignition in inertial confinement fusion. Moderate-$Z$ (MZ) materials (6 \textless\ $Z$ \textless\ 10) are expected to reduce both energy loss and hot-electron preheat due to the laser--plasma interaction. High-gain ignition designs for the National Ignition Facility (NIF) with MZ ablators are described and compared with a pure-plastic design. The NIF beam quads are split to irradiate the target with smaller laser focal spots during the main drive to reduce the losses caused by cross-beam energy transfer. Two-dimensional hydrodynamic simulations assess the robustness of these designs to the NIF specifications for target and laser nonuniformities including beam geometry, laser imprint, and ice and outer-surface roughness. Results indicate that MZ-ablator designs can achieve ignition for direct-drive implosions on the NIF. This material is based upon work supported by the Department of Energy National Nuclear Security Administration DE-NA0001944 and the Office of Science under DE-FC02-04ER54789.