Sources de particules avec des lasers de haute intensité: un outil pour les diagnostics plasma et une source innovante pour les applications.

This PhD dissertation is an experimental and theoretical study of particle generation by relativistic laser plasma interactions. In the first part of this manuscript, different mechanisms for neutron, electron as well as proton generation are presented and discussed for underdense and overdense plasmas. The second part is devoted to neutron generation by D(d,n)3He reactions as a diagnostic for the plasma ion temperature. The generation of an electron beam generated in the newly described "forced laser wakefield" regime is the issue for the third part. It is shown experimentally as well as theoretically that the utilization of a compact laser can result in an energetic and high quality electron beam. The last part shows that the same laser system can be implemented to generate a proton beam and that different acceleration mechanisms can yield in a proton beam. For any of the described particles several applications for accelerator physics, medical physics and the generation of secondary X rays will be discussed.Cette thèse de doctorat s'intègre dans le cadre des études tant expérimentales que théoriques sur la production et l'accélération de faisceaux de particules par interaction laser plasma en régime relativiste. Dans la première partie de ce mémoire, les différents mécanismes physiques à l'origine de la production de neutrons, d'électrons et de protons sont passés en revue et discutés. La deuxième partie s'intéresse à la production de neutrons par la réaction D(d,n)3He utilisée comme diagnostic de la température ionique d'un plasma sous dense. Lors de la production de faisceaux d'électrons à partir d'un faisceau laser ultra-court focalisé sur un jet de gaz, un nouveau régime d'accélération, le "sillage forcé", a été mis en évidence. Cette étude fait l'objet de la troisième partie. Il a été montré expérimentalement et théoriquement que l'utilisation d'un laser compact peut produire un faisceau d'électrons très énergétiques et de bonne qualité. La dernière partie est consacrée à la génération de faisceaux de protons avec une cible solide et mince à partir de la même chaîne laser. Pour chaque type de sources de particules, plusieurs applications sont discutées dans les domaines de la physique des accélérateurs, pour la physique médicale et pour la génération de rayonnement X par des processus secondaires

Numerical simulation of isotope production for positron emission tomography with laser-accelerated ions

International audienceThe experimental demonstration of laser acceleration of ions to multi-MeV energies with short, intense laser pulses has spurred the prospect of using this ion source for medical isotope production. Using numerical models for laser-plasma interaction and ion acceleration, then for ion transport and isotope production, we compute the isotope yields that could be expected from such sources, and their variations with interaction parameters such as target thickness and laser intensity. Using 36 fs, 4×10^20 W/cm^2 pulses at kilohertz repetition rate, more than 100 GBq of are expected after irradiation for 1 h

Femtosecond relativistic electron beam triggered early bioradical events

International audienceWith the recent advent of table-top terawatt Ti:Sa laser amplifier systems, laser plasma interactions provide high-energy, femtosecond electron bunches, which might conjecture direct observation of radiation events in media of biological interest. We report on the first femtolysis studies using such laser produced relativistic electron pulses in the 2.5-15 MeV range. A real-time observation of elementary radical events is performed on water molecules and media containing an important disulfide biomolecule. The primary yield of a reducing radical produced in clusters of excitation-ionisation events (spurs) has been determined at t~3.5 10^-12 s. These data provide important information about the initial energy loss and spatial distribution of early radical events. Femtolysis studies devoted to a disulfide biomolecule is noteworthy as it is the first time that a primary ionisation event can be controlled by an ultrafast radical anion formation in the prethermal regime. This innovating domain foreshadows the development of new applications in radiobiology (microdosimetry at the nanometric scale). In the near future, electron femtolysis studies would clearly enhance the understanding of radiation-induced damages in biological confined spaces (aqueous groove of DNA and protein pockets)

Numerical modeling and applications of laser-accelerated ion beams

International audienceWe use laser-plasma interaction and particle-transport codes to investigate ion acceleration when a short, intense laser pulse irradiates a thin solid foil, and to quantify the isotope yield that these ions can induce by nuclear reactions in secondary targets. Optimum acceleration, in terms of peak ion energy and secondary target activation, is obtained for ultra-low (sub-μm) target thickness

Electron Beam Production with an Ultra Short and Intense Laser Pulse: A New Tool for Scientists

International audienceBy focusing a 10 Hz, 30 TW, 30 fs laser beam onto a gas jet, it is now possible to produce an ultra short and high quality electron beam with a maximum energy of up to 200 MeV. The gas is instantaneously ionized by the laser electric field and transformed into plasma, in which accelerating electric fields of the order of 1 TV/m have been generated in the non-linear regime. Some applications of this attractive and compact electron source are presented