Laser Plasma Interactions at Shock Ignition Intensities and in NIF Direct Drive Ignition-Scale Ablation-Plasma Conditions*

Experiments performed at Omega and the National Ignition Facility have, for the first time, diagnosed laser plasma interactions and the associated hot-electrons at laser intensities of direct relevance to the Shock Ignition approach to laser fusion, and in the ablation plasma conditions expected for direct-drive NIF-ignition designs. The experiments indicate Stimulated Raman Scattering (SRS) is the dominant hot-electron production mechanism. Importantly, the measured hot-electron temperatures are sufficiently low that the hot-electrons should deposit their energy within the implosion shell in-flight, rather than pre-heating the fuel. This opens the possibility that hot-electrons will aid the shock-generation process. Large scale particle-in-cell simulations support the experimental findings.