| This thesis discusses two series of laser plasma interaction experiments, one carried out on the present 60-beam OMEGA glass laser facility, and the other one on the old 24-beam OMEGA laser facility. The process under study was stimulated Brillouin scattering (SBS) in long-scale-length plasmas such as might be expected in future breakeven or reactor size laser fusion experiments. The relevant plasmas have long gradient scale-lengths (typical scale lengths for density and velocity gradients {dollar}sim{dollar}1 mm) and electron temperatures of several keV. The plasmas were created by exploding thin, mass-limited targets with several sets of appropriately timed laser beams. A separate beam--the interaction beam--was then fired into those plasmas and the characteristic spectral signature of SBS was observed. The two sets of experiments distinguish themselves by the wavelength of the interaction beam (351-nm for the present 60-beam OMEGA, and 1053-nm for old 24-beam experiments). The interpretation of the experimental data is complex and several theoretical models have been developed. These models were compared with the experimental data with varying success. However, we believe that our results permit us to predict that future direct-drive laser plasma experiments will not be plagued by significant levels of SBS. |
