Extra ion feature of Thomson scattered light in the interaction of a 600 ps laser with helium gas jet

Abstract : The interaction of a 600 ps laser pulse at 0.53 μm wavelength with helium gas jet with an electron density of 8×10^19 cm^−3 has been studied. In this experiment the plasma parameters for density and temperature were well-defined via time-resolved Thomson scattering. Ion Thomson scattering measurements at 45° show two extra satellites which correspond to the rescattering of the Brillouin backscattered light off the thermal ion acoustic waves. Analysis of the relative amplitudes of these satellites gives a very high value of 65% of the instantaneous reflectivity at its maximum. Theoretical spectra are in good agreement with the experimental ones.