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Étude d'une cavité Fabry Pérot haute finesse à quatre miroirs pour des applications de production de rayons X et gamma par interaction Compton laser-électrons

Abstract : The main goal of this thesis focuses on the study and design of a high finesse Fabry Perot cavity to amplify a laser beam in order to achieve power gains ranging from 1E4 to 1E5. This cavity is dedicated to the production of intense and monochromatic X-ray for medical applications (medical RADIOTHOMX ring) and gamma rays, for Compton based polarized positron source of the "Compact Linear Collider" CLIC, and the "International Linear Collider " ILC, by Compton scattering of a high power laser beam and electron beam.
To increase the brightness of the Compton interaction at the collision points, it is essential to have not only a high power laser beam but also very small laser beam radii at the interaction points. To achieve such performances, two scenarii are possible: a concentric two mirrors cavity witch is mechanically unstable or a four mirrors cavity more complex but more stable. We tested numerically mechanical stability and stability of eigen modes polarization of various planar and non-planar geometries of four mirrors cavities. Experimentally, we have developed a four mirrors tetrahedral "bow-tie" cavity; radii of the order of 20 microns were made. The eigen modes of such a cavity, in both planar and non planar geometries, were measured and compared with the numerical results. A good agreement was observed.
In a second time, the impact of Compton interaction on the transverse dynamics, in the case of the source of polarized positrons source, and the longitudinal dynamic, in the case of the medical ring of the electron beam was studied. Compton scattering causes energy loss and induces an additional dispersion of energy in electron beam. For the polarized positrons source, ten collision points are planned. The transport line has been determined and modelling of the Compton interaction effect with a simple matrix calculation was made. For the medical ring, Compton scattering causes bunch lengthening and energy dispersion increase which are to influence the produced X-ray flux. A study of the longitudinal dynamics of the electron beam in the ring was presented. The parameters of the ring that optimize the brightness of the Compton interaction were discussed. The X-ray flux that can be achieved with these parameters is about 1E13 photons/s.
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Contributor : Yasmina Fedala <>
Submitted on : Friday, November 28, 2008 - 5:55:29 PM
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  • HAL Id : tel-00343028, version 1




Y. Fedala. Étude d'une cavité Fabry Pérot haute finesse à quatre miroirs pour des applications de production de rayons X et gamma par interaction Compton laser-électrons. Physique [physics]. Université Paris Sud - Paris XI, 2008. Français. ⟨tel-00343028⟩



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