Vol. 1, No 1, 1994 pp. 18 - 25
UDC 533.9.01

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NONLINEAR THEORY OF STIMULATED RAMAN BACKSCATTERING IN PLASMA
M.S. Jovanović¹ and M.M. Škorić^2
1Department of Physics, University of Niš, P.O. BOX 91, 18001 Niš, Yugoslavia
²Vinča Institute of Nuclear Sciences, P.O. BOX 522, 11001 Belgrade, Yugoslavia

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Abstract. The equations for slowly-varying amplitudes of the three waves taking part in the stimulated Raman backscattering are derived with the nonlinear frequency-shift effect incorporated. Temporal evolution of such a system is studied. When linear damping of electron plasma wave is small or absent, the behaviour is nonstationary in the sense the reflectivity coefficient pulsates irregularly in time. Above some critical damping value this incoherency is removed and asymptotic system behaviour is stationary. The mean reflectivity level in the incoherent regime turns out very low (typically under 10%), just as detected in recent experiments.

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NELINEARNA TEORIJA STIMULISANOG RAMANOVOG RASEJANJA UNAZAD U PLAZMI Izvedene su jednačine za sporo promenljive amplitude talasa u procesu stimulisanom Ramanovom rasejanju, pri čemu je uzet u obzir nelinearni frekventni pomeraj. Proučava se vremenska evolucija takvog sistema. Kada je linearno slabljenje elektronskog plazmenog talasa vrlo malo ili ga nema, ponašanje sistema je nestacionarno u smislu da koeficijent refleksije pulsira nepravilno u vremenu. Iznad neke kritične vrednosti slabljenja ova nekoherentnost nestaje i asimptotsko stanje sistema je stacionarno. Srednja reflektivnost u nekoherentnom režimu je vrlo niska (oko 10%), kao što je izmereno u nedavnim eksperimentima.