Localization of ionization-induced trapping in a laser wakefield accelerator using a density down-ramp

Hansson, Martin; Audet, T. L.; Ekerfelt, Henrik; Aurand, B.; González, I. Gallardo; Desforges, F. G.; Davoine, Xavier; Maitrallain, Antoine; Reymond, S.; Monot, P.; Persson, Anders; Dufrénoy, S. Dobosz; Wahlström, Claes‐Göran; Cros, B.; Lundh, Olle

doi:10.1088/0741-3335/58/5/055009

Cited by 14 publications

(15 citation statements)

References 22 publications

(39 reference statements)

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“…It also flattens and reduces the amplitude of the longitudinal field in the rear part of the bubble. However, the simulations performed for lower nitrogen concentrations (0.1% and 0.5%) agree with our previous study [21]. Along the plateau of the electron density distribution most of the accelerated charge comes from ionization-induced trapped electrons in the first plasma period.…”

Section: Calder-circ Simulationssupporting

confidence: 90%

“…Note that the parameter χ accounts for the percentage of nitrogen molecules in the gas mixture, and not for the percentage of K shell electrons with respect to the background electrons in the later formed plasma. Comparison of the accelerated electron beam parameters for nitrogen concentration of 0.0% (pure hydrogen) and 1.0% can be found in a previously published work [21].…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Together with the spatial overlap with the laser fields, electrons must be trapped in the plasma wave with significant transverse momentum in order to experience noticeable DLA [9,16]. Electrons can be self-trapped if the plasma wave becomes highly nonlinear and eventually breaks, but other trapping mechanisms have been developed [17][18][19][20][21]. In particular, the mixture of gases can lead to ionization-induced trapping by combining a low percentage of a high-Z gas dopant, such as nitrogen, with a low-Z gas, such as hydrogen [22,23].…”

Section: Introductionmentioning

confidence: 99%

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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: 90%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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“…The energy and divergence of the electron beam were calculated using the images of Lanex scintillation screen. The response of the full imaging system was calibrated using previously published calibration factors of 6.95 × 10 -8 pC/count for the scintillating screens measured at linear accelerator 48,49 . The betatron radiation was registered using the Andor iKon-L SO X-ray camera, sensitive to X-rays up to 20 keV.…”

Section: Methodsmentioning

confidence: 99%

Laser wakefield accelerated electron beams and betatron radiation from multijet gas targets

Tomkus

Girdauskas

Dudutis

et al. 2020

Sci Rep

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Laser Plasma Wakefield Accelerated (LWFA) electron beams and efficiency of betatron X-ray sources is studied using laser micromachined supersonic gas jet nozzle arrays. Separate sections of the target are used for the injection, acceleration and enhancement of electron oscillation. In this report, we present the results of LWFA and X-ray generation using dynamic gas density grid built by shock-waves of colliding jets. The experiment was done with the 40 TW, 35 fs laser at the Lund Laser Centre. Electron energies of 30–150 MeV and 1.0 × 108–5.5 × 108 photons per shot of betatron radiation have been measured. The implementation of the betatron source with separate regions of LWFA and plasma density grid raised the efficiency of X-ray generation and increased the number of photons per shot by a factor of 2–3 relative to a single-jet gas target source.

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“…Several techniques to improve the beam quality have been adopted e.g. the use of dual-stage targets of injector and accelerator [53,54], a combination of ionization and shock-front injection [55], ionization induced injection in a density down ramp [56] where quasi-monoenergetic electron beams have been observed.…”

Section: Introductionmentioning

confidence: 99%

Direct laser acceleration of electrons in a high-Z gas target and the effect of threshold plasma density on electron beam generation

Hazra

Moorti

Mishra

et al. 2019

Plasma Phys. Control. Fusion

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An experimental study of laser driven electron acceleration in N 2 and N 2 -He mixed gas-jet target using laser pulses of duration ~60-70 fs is presented. Generation of relativistic electron beam with quasi-thermal spectra was observed at a threshold density of ~1.6×10 18 cm -3 in case of pure N 2 , and the threshold density was found to increase with increasing doping concentration of He.At an optimum fraction of 50% of He in N 2, generation of quasi-monoenergetic electron beams was observed at a comparatively higher threshold density of ~2×10 18 cm -3 , with an average peak energy of ~168 MeV, average energy spread of ~21%, and average total beam charge of ~220 pC. Electron acceleration could be attributed to the direct laser acceleration as well as the hybrid mechanism. Observation of an optimum fraction of He in N 2 (in turn threshold plasma density) for comparatively better quality electron beam generation could be understood in terms of the plasma density dependent variation in the dephasing rate of electrons with respect to transverse oscillating laser field. Results are also supported by the 2D PIC simulations performed using code EPOCH.

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Localization of ionization-induced trapping in a laser wakefield accelerator using a density down-ramp

Cited by 14 publications

References 22 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

Laser wakefield accelerated electron beams and betatron radiation from multijet gas targets

Direct laser acceleration of electrons in a high-Z gas target and the effect of threshold plasma density on electron beam generation

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