Étude du comportement collectif des speckles dans le développement de la diffusion Raman stimulée lors de l’interaction laser-plasma

Abstract : Laser-plasma instabilities which occur in millimetric hot plasma, typical in ICF experiments, are still a preoccupying topic because they lead to reflectivity levels higher than predicted. In this context, this work focuses on stimulated Raman scattering (SRS) through a multi-scale analysis: mono, bi and multi speckle scales. This picosecond experimental study highlights the difference between isolated and collective speckle behaviors in SRS development. A weak speckle, stable if isolated, may become unstable under the influence of SRS driven local plasma modifications generated by an intense nearby speckle: kinetic perturbations with suprathermal electrons and/or wave coupling with electromagnetic and electrostatic seeds. From set of experimental campaigns, featuring a highly spatially- and temporally-resolved Thomson-scattering diagnostic and backward Raman imaging, we evidenced and characterized this collective behavior. An experimental difference between these two kinds of perturbations was observed which lead to differentiate their contributions. In parallel, 2D PIC simulations using CALDER were performed to interpret bispeckle experimental results and in particular to understand the influence from both kinds of perturbations.
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Submitted on : Wednesday, March 16, 2016 - 1:32:58 PM
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  • HAL Id : tel-01226783, version 2

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Kevin Glize. Étude du comportement collectif des speckles dans le développement de la diffusion Raman stimulée lors de l’interaction laser-plasma. Physique des plasmas [physics.plasm-ph]. Ecole Polytechnique, 2015. Français. ⟨tel-01226783v2⟩

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