Recent experiments at the National Ignition Facility and the SG-II Upgrade facility have shown that stimulated Raman side scattering (SRSS) can significantly degrade laser-plasma coupling and generate substantial hot-electron fluxes in direct-drive inertial confinement fusion. However, SRSS remains poorly understood, particularly in its dependence on the laser beam diameter D. Previous simulations has shown that the SRSS gain increases monotonically with D, in clear disagreement with conventional theories. Here we investigate the role of a common-wave process in SRSS in nonuniform plasma. Fluid simulations indicate that scattered light can couple through a common electron plasma wave, enabling transverse growth of scattered-light intensity across the focal spot beyond the convective saturation length limit. The implications of common-wave process for SRSS development and its dependence on beam diameter will be presented.
 

inertial confinement fusion,laser plasma instabilities