Modeling Crossed-Beam Energy Transfer in Implosion Experiments on OMEGA

Scattered-light measurements in direct-drive-implosion experiments on the OMEGA Laser System indicate enhanced light scattering in comparison with radiative-hydrodynamic simulations that include inverse bremsstrahlung as the primary absorption mechanism of the laser light. Beam-to-beam energy transfer caused by stimulated Brillouin scattering (SBS) is likely responsible for the reduction in absorbed energy at the end of drive pulses in OMEGA implosions. We have developed a simplified model for crossed-beam energy transfer that accounts for the propagation and coupling of multiple laser beams and associated plasma waves in spherically symmetric plasmas. This model has been implemented in the radiative-hydrodynamic code \textit{LILAC}, demonstrating effects of SBS in implosion experiments on OMEGA. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302.