Observation of polarization dependent Raman scattering in a large scale plasma illuminated with multiple laser beams

• Published in: Physics of plasmas 2006-08, Vol.13 (8)
• Main Authors: Kirkwood, R K, Moody, J D, Niemann, C, Williams, E A, Langdon, A B, Landen, O L, Divol, L, Suter, L J, Depierreux, S, Seka, W, Departement de Conception et de Realisation des Experimentations, CEA-DIF, BP12, 91680 Bruyeres-le-Chatel, Laboratory of Laser Energetics, University of Rochester, Rochester, New York 14627
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ICF DEVICES; INERTIAL CONFINEMENT; LASER-PRODUCED PLASMA; LASERS; LIGHT TRANSMISSION; NONLINEAR PROBLEMS; PLASMA HEATING; POLARIZATION; PONDEROMOTIVE FORCE; RAMAN EFFECT; THERMONUCLEAR IGNITION
• ISSN: 1070-664X; 1089-7674

Experiments in plasmas produced with 2 mm diameter gas filled targets preheated with 10 kJ of laser energy have shown that the stimulated Raman scattering (SRS) of a high intensity, 351 nm, beam is affected by the presence of a second, counterpropagating, high intensity beam and that has its polarization aligned to the first when the plasma conditions are relevant to ignition by indirect drive. Separate experiments with the crossing beam's polarization rotated to be normal to the first beam's polarization show little change in the SRS backscatter when the second beam is added, consistent with the reduction in the SRS being caused by low frequency waves driven by the ponderomotive force produced by the beating of the two beams.