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Autoresonance in Stimulated Raman Scattering

Abstract : Stimulated Raman scattering (SRS) is studied in plasmas relevant to inertial confinement fusion (ICF) experiments. The excitation of autoresonant Langmuir waves in inhomogeneous plasmas is investigated as a mechanism for the enhancement of SRS in the kinetic regime (k_L*lambda_D>0.25). It is shown that weakly kinetic effects like electron trapping, described via an amplitude-dependent frequency shift, may compensate the dephasing of the three-wave resonance of SRS that normally occurs in inhomogeneous plasmas. Under conditions relevant to current and future ICF experiments (National Ignition Facility, Laser Mégajoule), a simple analytical model is found to predict to good accuracy the observed growth, saturation and phase of Langmuir waves, in both three-wave coupling and kinetic (particle-in-cell) simulations. Through autoresonance, observed SRS levels far exceed the spatial amplification expected from Rosenbluth's model in an inhomogeneous profile [M. N. Rosenbluth, Phys. Rev. Lett. 29, 565 (1972)]. A potential application of autoresonance is proposed in the form of a Raman amplifier.
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https://pastel.archives-ouvertes.fr/pastel-00674111
Contributor : Thomas Chapman <>
Submitted on : Saturday, February 25, 2012 - 4:25:44 AM
Last modification on : Wednesday, March 27, 2019 - 4:02:05 PM
Long-term archiving on: : Saturday, May 26, 2012 - 2:20:32 AM

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  • HAL Id : pastel-00674111, version 1

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Chapman Thomas. Autoresonance in Stimulated Raman Scattering. Plasma Physics [physics.plasm-ph]. Ecole Polytechnique X, 2011. English. ⟨pastel-00674111⟩

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