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Modélisation théorique et numérique de la saturation de l'instabilité de diffusion Raman stimulée se développant dans l'interaction laser-plasma.

Abstract : Let us begin by recalling that the objective of the thesis was twofold: - Digital: it was to develop a code capable of simulating the saturation of the instability of stimulated Raman scattering (SRS) through the coupling with the ion acoustic waves in a fluid description, homogeneous and inhomogeneous plasma and multidimensional geometry. The model chosen is based on a system composed of equations like the equations for paraxial electromagnetic type for Zakharov equation of Langmuir waves and sound waves. The problem was addressed in an open environment where, unlike a periodic medium, the definition of boundary conditions has to be robust without the digital artifacts introduced distorting the physical results, including inhomogeneous plasma where the presence of points Dish is able to destabilize the absolute instability, which adds a "difficulty" additional significant. - Physical: it was to analyze the mechanisms of nonlinear saturation of the Raman instability and establish the extent possible, scaling laws. In order to test the potential and limitations of our code, we chose to focus specifically on the regime kLλDe ~ 0.2 (where kL is the wave number of the fundamental wave generated by the Langmuir instability and Raman λDe the electronic Debye length). This regime is the regime most certainly difficult to study in the sense that it is intermediate between the extreme regimes (i) = 0.1 kLλDe with the presence of cavitation and (ii) kLλDe = 0.3 which gives a strong Landau damping and electronic kinetic effects, and therefore all processes are suceptible to grow, as we have actually observed.
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Submitted on : Wednesday, July 28, 2010 - 3:52:04 PM
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Thomas Fouquet. Modélisation théorique et numérique de la saturation de l'instabilité de diffusion Raman stimulée se développant dans l'interaction laser-plasma.. Physique [physics]. Ecole Polytechnique X, 2007. Français. ⟨pastel-00002323⟩

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