Stable multi-GeV electron accelerator driven by waveform-controlled PW laser pulses

Abstract : The achievable energy and the stability of accelerated electron beams have been the most critical issues in laser wakefield acceleration. As laser propagation, plasma wave formation and electron acceleration are highly nonlinear processes, the laser wakefield acceleration (LWFA) is extremely sensitive to initial experimental conditions. We propose a simple and elegant waveform control method for the LWFA process to enhance the performance of a laser electron accelerator by applying a fully optical and programmable technique to control the chirp of PW laser pulses. We found sensitive dependence of energy and stability of electron beams on the spectral phase of laser pulses and obtained stable 2-GeV electron beams from a 1-cm gas cell of helium. The waveform control technique for LWFA would prompt practical applications of centimeter-scale GeV-electron accelerators to a compact radiation sources in the x-ray and γ-ray regions. Laser wakefield electron accelerators 1 have strong potential for a next generation accelerator due to its huge acceleration field. Laser wakefield acceleration (LWFA) has been intensively investigated to produce quasi-mono-energetic collimated GeV electron beams in centimeter-scale acceleration length 2–4. Recent progresses of LWFA demonstrated quasi-mono-energetic electron beams in the hundreds MeV range that are produced in a stable way by utilizing methods such as colliding laser pulses 5, 6 , ionization injection 7–10 and density gradient injection 11–14 with an improvement of the stability that results from explored injection schemes. Here we propose a simple method to enhance the energy and the stability of multi-GeV electron beams 15–17 by controlling the waveform of PW laser pulses using a fully optical, programmable method 18–20. LWFA is based on the interaction between an underdense plasma and an intense laser pulse. The interaction between a driving laser pulse and a plasma in LWFA is a complex process occurring in the relativistic regime, because the formation of plasma waves and electron acceleration processes are highly nonlinear while the propagating laser pulse is strongly modified by the medium 21, 22. The LWFA is, thus, very sensitive to the initial properties of driving laser pulse, and the waveform of the laser pulse can significantly affect the LWFA process. The waveform control technique brought significant advancement of light-matter interactions by realizing coherent control 23, 24 of a chemical reaction or atomic excitation/ionization. In the coherent control of a quantum system, the probability of a certain reaction or excitation/ionization pathway can be selectively enhanced by controlling the waveform of a driving laser pulse. Here, we propose and demonstrate that the LWFA can be optimized by controlling the waveform of the driving laser pulse so as to enhance the energy and the stability of accelerated electron beams; the laser-plasma interaction in the LWFA is strongly affected by the coherent property of the laser pulse.
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Scientific Reports, Nature Publishing Group, 2017, 7 (1), 〈10.1038/s41598-017-09267-1〉
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Dernière modification le : jeudi 10 mai 2018 - 01:58:42

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Hyung Taek Kim, V. Pathak, Ki Hong Pae, Agustin Lifschitz, François Sylla, et al.. Stable multi-GeV electron accelerator driven by waveform-controlled PW laser pulses. Scientific Reports, Nature Publishing Group, 2017, 7 (1), 〈10.1038/s41598-017-09267-1〉. 〈hal-01599420〉

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