Reduction of stimulated scattering losses from hohlraum plasmas with laser beam smoothing

Laser beam smoothing by spectral dispersion and by polarization smoothing has been observed to significantly reduce the scattering losses by stimulated Brillouin and stimulated Raman scattering from inertial confinement fusion hohlraums. For these measurements, the laser beam smoothing and the high-Z hohlraum wall plasma parameters approach the conditions of future inertial confinement fusion experiments. The simultaneous application of the smoothing techniques has reduced the scattering losses by almost one order of magnitude down to the 1% level. The experimental scaling of the stimulated Brillouin reflectivity compares well to modeling assuming nonlinear damping on the ion acoustic waves in three-dimensional nonlinear wave simulations and calculated hohlraum plasma conditions from radiation-hydrodynamic modeling.