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Etude théorique et numérique de l'expansion d'un plasma crée par laser : accélération d'ions à haute énergie.

Abstract : This PhD dissertation is a theoretical and numerical study on the high energy ion acceleration in laser created plasma expansion. The ion beams produced on the rear side of an irradied foil reveal some characteristics (laminarity, low divergence, wide spectra) which distinguinsh them from the ones coming from the front side. The discovery of these beams has renewed speculation for applications such as protontherapy or proton radiography. The ion acceleration is performed via a self-consistent electrostatic field due to the charge separation between ions and hot electrons. In the first part of this dissertation, we present the fluid theoretical model and the hybrid code which simulates the plasma expansion. The numerical simulation of a recent experience on the dynamic of the electric field by proton radiography validates the theoritical model. The second part deals with the inuence of an initial ion density gradient on the acceleration efficiency. We establish a model which relates the plasma dynamic and more precisely the wavebreaking of the ion flow. The numerical results which predict a strong decrease of the ion maximum energy for large gradient length are in agreement with the experimental data. The Botzmann equilibrium for the electron assumed in the first part has been thrown back into doubt in the third part. We adopt a kinetic description for the electron. The new version of the code can mesure the Boltzmann law deviation which does not strongly modify the maximum energy that can reach the ions.
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Submitted on : Tuesday, July 27, 2010 - 9:34:00 AM
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Thomas Grismayer. Etude théorique et numérique de l'expansion d'un plasma crée par laser : accélération d'ions à haute énergie.. Physique [physics]. Ecole Polytechnique X, 2006. Français. ⟨pastel-00002924⟩

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