Etudes d'amplificateurs plasma laser à haute cadence dans le domaine X-UV.

Abstract : The progress made as well on the Ti:Sa laser system, as in the control and the knowledge of laser produced XUV sources allowed the construction of a XUV laser station dedicated to the applications in the Université Paris XI. My thesis work falls under the development of this station and more particularly on the characterization of a XUV laser plasma amplifier.
The experimental study relates to the coupling improvement of the pump infra-red laser with plasma within the framework of the transient collisional XUV laser generation. These XUV lasers are generated in a plasma formed by the interaction of a solid target and a laser pulse of approximately 500 ps duration, followed by a second infra-red laser pulse known as of pump (~5 ps) impinging on the target in grazing incidence. For the first time, a complete parametric study was undertaken on the influence of the grazing angle on the pumping of the amplifying medium. One of the results was to reach very high peak brightness about 1 x 10^{28} ph/s/mm²/mrad²/(0.1% bandwidth), which compares well with the free electron laser brightness. Moreover, we modified then used a new two-dimensional hydrodynamic code with adaptive mesh refinement in order to understand the influence of the space-time properties of the infra-red laser on the formation and the evolution of the amplifying plasma. Our modelings highlighted the interest to use a super Gaussian transverse profile for the line focus leading to an increase in a factor two of the gain region size and a reduction of the electron density gradient by three orders of magnitude. These improvements should strongly increase the energy contained in XUV laser beam.
The knowledge improvement of materials physic or biomolecules behaviour will benefit from the tool that the XUV laser radiation field is on the way to become. We thus used XUV laser to study the appearance of transient defects produced by a laser IR on a beam-splitter rear side. We also began research on the mechanisms of DNA damage induced by a very intense XUV radiation.
Document type :
Physique Atomique [physics.atom-ph]. Université Paris Sud - Paris XI, 2006. Français
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Kevin Cassou. Etudes d'amplificateurs plasma laser à haute cadence dans le domaine X-UV.. Physique Atomique [physics.atom-ph]. Université Paris Sud - Paris XI, 2006. Français. 〈tel-00170172〉



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