STIMULATED BRILLOUIN-SCATTERING WITH A 1 PS LASER-PULSE IN A PERFORMED UNDERDENSE PLASMA

An experimental study of stimulated Brillouin scattering (SBS) with a 1 ps laser pulse in a large underdense preformed plasma is presented. It is shown that the SBS reflectivity increases from 10(-4) to 10(-1) as the intensity of the interaction beam rises from 5 x 10(14) to 10(16) W/cm2; for intensities between 10(16) and 10(17) W/CM2, a saturation level at 10% is experimentally established. This experimental result is compared with theoretical estimates of time-integrated SBS reflectivity in the transient phase of the so-called modified decay regime. The latter results are seen to be consistent with the experimental data provided that there exists a nonthermal noise in the plasma depending on the laser intensity.