01 Décembre – Thesis defense - Victorien Bouffetier

14 h Amphi B - building A29 (Talence campus)

Development of interferometric X-Ray phase contrast imagery and application to the caracterisation of dense turbulents plasmas.

The raise of high power laser facilities in the second half of the XXth century, enabled the capability to study the matter in extreme conditions of pressure and temperature. The applications of thermonuclear fusion and laboratory astrophysics is then rapidly raised. The elements used in such experiments usually being with a low atomic number Z, their absorption is usually weak, thus offering poor contrast at radiography. New more refined methods to image such media are then needed.
To describe the behavior of light going through matter, one can use the complex optical index of a medium. The real part of this index governs the refraction while the complex part enables one to describe the absorption by the medium. In low Z materials, when photons are in the energy range of 1 to 100 keV, the real part of the index is usually stronger than the complex one. This property is therefore of interest for the development of X-ray phase imaging capabilities of such media.
We propose in this manuscript to study the propagative and interferometric phase imaging methods for laser generated plasmas at XFEL and laser facilities. Firstly, is recalled the basics of plasma and imaging physics necessary to develop X-ray phase contrast imaging in this context. Secondly are presented the facilities and main diagnostics used in our studies. Then we show our results using propagative imaging methods at laser and XFEL facilities. The manuscript finishes by dealing with the current developments of differential X-ray phase contrast imaging of laser generated plasmas using a Talbot-Lau X-ray interferometer. We also show its first demonstration at XFEL facilities to image and diagnose laser generated plasmas in a HED framework.

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