Bremsstrahlung Measurements of the Properties of Laser-Generated Hot Electrons for Fast Ignition*

The laser to hot electron coupling efficiency, divergence angle, and spectrum are the key parameters for evaluating whether a compressed fusion capsule will ignite under the Fast Ignition scheme for Inertial Confinement Fusion. These properties were studied on the Titan laser (1054 nm, 150 J, 0.7 ps, 10$^{20}$ W/cm$^2$) at LLNL using an array of absolutely calibrated Bremsstrahlung spectrometers (differential sensitivity up to 700 keV) measuring emission from planar multilayer foil and cone-foil targets. A HOPG crystal spectrometer was also used to measure the line emission from buried flours. The electron transport and x-ray emission is modeled with the Monte Carlo code ITS 3.0 and the hybrid-PIC code LSP LLNL-ABS-45809