Effect of experimental laser imperfections on laser wakefield acceleration and betatron source

Ferri, Julien; Davoine, Xavier; Fourmaux, S.; Kieffer, Jean‐Claude; Corde, S.; Phuoc, K. Ta; Lifschitz, Agustín

doi:10.1038/srep27846

Cited by 33 publications

(27 citation statements)

References 33 publications

(41 reference statements)

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“…The fact that the simulated laser pulse has a Gaussian temporal and spatial distribution implies a more efficient self-compression and self-focusing than for our real laser pulse. This produces a stronger wakefield that can increase the total accelerated charge and energy of accelerated electrons when comparing with the experimental results [29]. We believe that this might originate the mismatch of accelerated charge and maximum electron energy between simulations and the experiment, but the trend of the charge above a certain energy threshold for different concentrations qualitatively reproduces the experimental observations.…”

Section: Calder-circ Simulationssupporting

confidence: 58%

Effects of the dopant concentration in laser wakefield and direct laser acceleration of electrons

et al. 2018

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In this work, we experimentally study the effects of the nitrogen concentration in laser wakefield acceleration of electrons in a gas mixture of hydrogen and nitrogen. A 15 TW peak power laser pulse is focused to ionize the gas, excite a plasma wave and accelerate electrons up to 230 MeV. We find that at dopant concentrations above 2% the total divergence of the electrons is increased and the high energy electrons are emitted preferentially with an angle of±6 mrad, leading to a forked spatio-spectral distribution associated to direct laser acceleration (DLA). However, electrons can gain more energy and have a divergence lower than 4 mrad for concentrations below 0.5% and the same laser and plasma conditions. Particle-in-cell simulations show that for dopant concentrations above 2%, the amount of trapped charge is large enough to significantly perturb the plasma wave, reducing the amplitude of the longitudinal wakefield and suppressing other trapping mechanisms. At high concentrations the number of trapped electrons overlapping with the laser fields is increased, which rises the amount of charge affected by DLA. We conclude that the dopant concentration affects the quantity of electrons that experience significant DLA and the beam loading of the plasma wave driven by the laser pulse. These two mechanisms influence the electrons final energy, and thus the dopant concentration should be considered as a factor for the optimization of the electron beam parameters.

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Section: Calder-circ Simulationssupporting

confidence: 58%

Effects of the dopant concentration in laser wakefield and direct laser acceleration of electrons

et al. 2018

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“…If applied directly in an experiment such a spot is applicable for simulation purposes. Note that other methods can also be used to retrieve beam profiles using experimental inputs, such as the Gerchberg-Saxton algorithm [55] which was, for example, used for laser wakefield simulations with realistic laser profiles [56]. Alternatively, the experimental focus can be optimized with the help of our method coupled with machine learning techniques and using the measured beam profile before focusing and focal spot.…”

Section: Focusing Of Realistic Laser Pulsesmentioning

confidence: 99%

Optimized Computation of Tight Focusing of Short Pulses Using Mapping to Periodic Space

et al. 2021

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When a pulsed, few-cycle electromagnetic wave is focused by optics with f-number smaller than two, the frequency components it contains are focused to different regions of space, building up a complex electromagnetic field structure. Accurate numerical computation of this structure is essential for many applications such as the analysis, diagnostics, and control of high-intensity laser-matter interactions. However, straightforward use of finite-difference methods can impose unacceptably high demands on computational resources, owing to the necessity of resolving far-field and near-field zones at sufficiently high resolution to overcome numerical dispersion effects. Here, we present a procedure for fast computation of tight focusing by mapping a spherically curved far-field region to periodic space, where the field can be advanced by a dispersion-free spectral solver. In many cases of interest, the mapping reduces both run time and memory requirements by a factor of order 10, making it possible to carry out simulations on a desktop machine or a single node of a supercomputer. We provide an open-source C++ implementation with Python bindings and demonstrate its use for a desktop machine, where the routine provides the opportunity to use the resolution sufficient for handling the pulses with spectra spanning over several octaves. The described approach can facilitate the stability analysis of theoretical proposals, the studies based on statistical inferences, as well as the overall development and analysis of experiments with tightly-focused short laser pulses.

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“…4(c)], reaching a maximal value of 45.8 keV for α = 3 • . Such a boost of the X-ray critical energy shall be of strong interest for medical applications, making the 10's of keV energy range accessible to a 1.5 Joule laser beam without aberrations 25 . Note however that whereas this scheme conserves the ultra-short duration of the betatron source, the amplified transverse motion will increase the source divergence in the direction of the gradient, as the divergence is directly proportionnal to r β .…”

Section: Betatron Radiationmentioning

confidence: 99%

Enhancement of betatron x rays through asymmetric laser wakefield generated in transverse density gradients

Ferri

Davoine

2018

Phys. Rev. Accel. Beams

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Laser wakefield acceleration of electrons usually offers an axisymmetry around the laser propagation axis. Thus, the accelerating electrons that are focused on axis often execute small transverse oscillations. In this Article, we propose a simple scheme to break this symmetry, which enhances the transverse wiggling of electrons and boosts the betatron radiation emission. Through 3D particle-in-cell simulations, we show that sending the laser with a small angle of incidence on a transverse plasma density gradient generates an asymmetric wakefield. It first provokes injection and then increases the wiggling of the electrons through the transverse shifting of the wakefield axis which occurs when the laser pulse leaves the gradient. Consequently, we show that the radiated energy per unit of charge can increase by a factor > 20 when using this scheme, and that the critical energy of the radiation quintuples compared with a reference case without the transverse density gradient.

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Effect of experimental laser imperfections on laser wakefield acceleration and betatron source

Cited by 33 publications

References 33 publications

Effects of the dopant concentration in laser wakefield and direct laser acceleration of electrons

Effects of the dopant concentration in laser wakefield and direct laser acceleration of electrons

Optimized Computation of Tight Focusing of Short Pulses Using Mapping to Periodic Space

Enhancement of betatron x rays through asymmetric laser wakefield generated in transverse density gradients

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