Reduction of stimulated scattering losses from hohlraum plasmas with laserbeam smoothing

Laser beam smoothing by spectral dispersion and by polarization smoothing h as been observed to significantly reduce the scattering losses by stimulate d Brillouin and stimulated Raman scattering from inertial confinement fusio n hohlraums. For these measurements, the laser beam smoothing and the high- Z hohlraum wall plasma parameters approach the conditions of future inertia l confinement fusion experiments. The simultaneous application of the smoot hing techniques has reduced the scattering losses by almost one order of ma gnitude down to the 1% level. The experimental scaling of the stimulated Br illouin reflectivity compares well to modeling assuming nonlinear damping o n the ion acoustic waves in three-dimensional nonlinear wave simulations an d calculated hohlraum plasma conditions from radiation-hydrodynamic modelin g. (C) 2001 American Institute of Physics.