TIME-DEPENDENT FILAMENTATION AND STIMULATED BRILLOUIN FORWARD SCATTERING IN INERTIAL CONFINEMENT FUSION PLASMAS

Numerical simulations of the temporal evolution of laser light filamen tation and stimulated Brillouin forward scattering (SBFS); in plasmas, under conditions that are relevant to laser fusion, are presented and analyzed. Long term unsteady behavior of filaments is observed to be the norm. Temporal and spatial incoherence due to filamentation and SB FS are impressed upon time-independent incident laser beams. The bandw idth and angular divergence imposed upon the beam increase with the st rength of the interaction. In addition, the spectrum of the transmitte d light is redshifted by an amount that increases with the interaction strength. Spectral analysis of the transmitted light reveals that SBF S plays a role in the generation of the observed temporal incoherence. Incident beams with some spatial incoherence but no temporal smoothin g are compared to those with ab initio temporal beam smoothing (TBS). Under typical conditions, TBS beams will undergo far less angular and spectral spreading and far less SBFS than unsmoothed beams.