An Implosion-Velocity Survey for Shock Ignition at the National Ignition Facility

Shock ignition (SI) is a low-energy, high-gain alternative path to ignition at the National Ignition Facility (NIF). In SI, a high-intensity laser spike added at the end of the compression pulse launches a strong shock into the precompressed capsule, raising the hot-spot pressure and temperature. This spike pulse allows SI targets to achieve ignition temperatures at lower shell velocities than standard hot-spot implosions. Optimizing the ignition margin in SI implosions requires finding an implosion velocity that balances 1-D target performance with multidimensional stability characteristics. Polar-drive SI designs for the NIF at 700 kJ will be reviewed and compared for stability and margin in 1-D and 2-D simulations at implosion velocities varying from 260 to 300 km/s. Stability studies will include both polar-drive beam geometry and beam repointing as well as laser-imprinted nonuniformities from laser speckle. 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.