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Etude expérimentale de l'interaction d'un laser Terawatt avec un plasma sous-dense:
production d'une source brillante et courte d'électrons relativistes

Abstract : This PhD. dissertation is an experimental study in the context of laser-plasma interaction in the relativistic regime. The coupling of the laser to the plasma causes numerous nonlinear phenomena such as relativistic self-focusing, Raman instabilities, wakefield generation and the breaking of plasma waves. In this self-modulated laser wakefield regime, these effects combine and accelerate background plasma electrons to relativistic velocities. In the first part of the dissertation, nonlinear effects are studied. A new method based on chirped laser pulses allowed us to measure the dynamics of Raman instabilities. The results show that backward Raman scattering occurs at the front of the pulse while forward Raman scattering occurs at the back. In addition, laser self-focusing was studied using shadowgraphy. The results show that the laser power is not the only important parameter for self-focusing: the laser pulse duration must be compared to plasma particle motion times: $\omega_p^{-1}$ for electrons and $\omega_{pi}^{-1}$ for ions. In particular, when the pulse duration is too short, relativistic self-focusing does not occur. The second part of the dissertation discusses the production of a relativistic electron source (0 à 70 MeV) using a 10 Hz laser (35 fs, 600 mJ). This bright ($10^{10}$ electrons) electron source was characterized experimentally: it has a Maxwell-like velocity distribution and is potentially short(<100 fs). The source is now available for applications. Finally, the third part deals with experiments which explore electron acceleration up to GeV energies. Specifically, we discuss the guiding of a Terawatt pulse in a plasma channel and the creation of centimeter long plasmas in rectangular and supersonic gas jets.
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https://pastel.archives-ouvertes.fr/tel-00404299
Contributor : Jérôme Faure <>
Submitted on : Thursday, July 16, 2009 - 10:36:35 AM
Last modification on : Wednesday, July 3, 2019 - 10:48:01 AM
Long-term archiving on: : Tuesday, June 15, 2010 - 6:28:45 PM

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  • HAL Id : tel-00404299, version 1

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Jérôme Faure. Etude expérimentale de l'interaction d'un laser Terawatt avec un plasma sous-dense:
production d'une source brillante et courte d'électrons relativistes. Physique [physics]. Ecole Polytechnique X, 2001. Français. ⟨tel-00404299⟩

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