Direct-Drive Inertial Confinement Fusion Implosions on Omega

Direct-drive inertial confinement fusion (ICF) creates extreme states of matter. In current direct-drive cryogenic target implosions on the 60-beam OMEGA laser system, the compressed target has a measured pressure of 5 Gbar. These targets are hydrodynamically scaled from ignition targets for the National Ignition Facility. The ignition targets are predicted to have peak pressures of 3 Tbar after the target ignites. ICF target acceleration and deceleration are realized when hot, low-density plasma pushes against cold, high-density plasma, making the target implosion inherently susceptible to the Rayleigh–Taylor hydrodynamic instability (RTI). The unstable RTI growth causes mixing of cold, high-density shell plasma with the low-density, hot-spot plasma and reduces the primary neutron yield of the implosion. The strategy to control the RTI growth is to reduce the seeds (e.g., laser imprint and target-surface roughness) and the growth rates of the dominant modes. This paper reports on our recent experiments, progress in validating the hydrodynamics codes that are used to design future high-gain cryogenic DT targets, and techniques to improve target performance. A brief description is given of a new high energy petawatt laser – OMEGA EP (extended performance) – that is being added to the OMEGA compression facility.