Spherical shock-ignition experiments with the 40+20-beam configuration on OMEGA

Spherical shock-ignition experiments on OMEGA used a novel beam configuration that separates low-intensity compression beams and high-intensity spike beams. Significant improvements in the performance of plastic-shell, D-2 implosions were observed with repointed beams. The analysis of the coupling of the high-intensity spike beam energy into the imploding capsule indicates that absorbed hot-electron energy contributes to the coupling. The backscattering of laser energy was measured to reach up to 36% at single-beam intensities of similar to 8 x 10(15) W/cm(2). Hard x-ray measurements revealed a relatively low hot-electron temperature of similar to 30 keV independent of intensity and timing. At the highest intensity, stimulated Brillouin scattering occurs near and above the quarter-critical density and the two-plasmon-decay instability is suppressed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4763556]