Improvement of laser-wakefield accelerators: towards a compact free electron laser

Abstract : When an intense and short laser pulse propagates through an underdensegas, it can accelerate a fraction of the electrons of the gas, andthereby generate an electron bunch with an energy of a few hundreds ofMeV. This phenomenon, which is referred to as laser-wakefield acceleration, has many potential applications, including the design of ultra-bright X-ray sources known as freeelectron lasers (FEL). However, these applications require the electronbunch to have an excellent quality (low divergence, emittance andenergy spread). In this thesis, different solutions to improve thequality of the electron bunch are developed, both analytically and through the use of Particle-In-Cell (PIC) simulations. It is first shown however that PIC simulations tend to erroneously overestimate the emittance of the bunch, due to the numerical Cherenkov effect. Thus, in order to correctly estimate the emittance, a modified PICalgorithm is proposed, which is not subject to this unphysical Cherenkov effect. Using this algorithm, we observed and studied a new mechanism togenerate the electron bunch: optical transverse injection. This mechanism can produce bunches with ahigh charge, a low emittance and a low energy spread. In addition, wealso proposed an experimental setup - the laser-plasma lens- which can strongly reduce the final divergence of the bunch.Finally, these results are put into context by discussing the propertiesrequired for the design of a compact FEL. It is shown in particularthat laser-wakefield accelerator could be advantageously combinedwith innovative laser-plasma undulators, in order to produce brightX-rays sources.
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Contributor : Remi Lehe <>
Submitted on : Thursday, November 27, 2014 - 8:36:50 PM
Last modification on : Wednesday, March 27, 2019 - 4:42:28 PM
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  • HAL Id : tel-01088398, version 1



Rémi Lehe. Improvement of laser-wakefield accelerators: towards a compact free electron laser. Plasma Physics [physics.plasm-ph]. Ecole Polytechnique, 2014. English. ⟨tel-01088398⟩



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