NEAR-FORWARD SCATTERING OF LASER-LIGHT

Near-forward scattering of laser light in a plasma, in regimes relevant to future inertial-confinement-fusion (ICF) experiments, has been investigated experimentally. The intensity scaling of stimulated Raman scattering (SRS) forward scattering at one angle was measured from a low-Z plasma. It was found that the intensity threshold and scaling were consistent with convective theory. Forward SRS saturated at a relatively low intensity. In a second experiment using Ti plasmas, absolutely calibrated, time-resolved stimulated Brillouin scattering (SBS) spectra from up to seven different angles were measured simultaneously. It was found that the angular dependence of the scattered energy was qualitatively consistent with convective theory. The spectra provided. the first evidence of near-forward SBS. Contrary to previous estimates, near-forward SBS was shown to be more efficient than oblique backscattering and may be an important effect for ICF.