Generation of Stable, Low-Divergence Electron Beams by Laser-Wakefield Acceleration in a Steady-State-Flow Gas Cell

Osterhoff, Jens; Popp, Antonia; Major, Zsuzsanna; Marx, Benjamin; Rowlands-Rees, T. P.; Fuchs, M.; Geissler, Michael; Hörlein, Rainer; Hidding, B.; Becker, Stefan; Peralta, E. A.; Schramm, U.; Grüner, F.; Habs, D.; Krausz, Ferenc; Hooker, S. M.; Karsch, Stefan

doi:10.1103/physrevlett.101.085002

Cited by 210 publications

(147 citation statements)

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“…At a plasma density of n p = 8 × 10 18 cm −3 , electron bunches with an overall charge of 7 pC are injected into the laser wakefield and accelerated to energies of up to ∼210 MeV (ref. 10). The average beam divergence after collimation with the magnetic lenses is 0.7 mrad with an r.m.s.…”

Section: Methodsmentioning

confidence: 99%

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Laser-driven soft-X-ray undulator source

et al. 2009

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Synchrotrons and free-electron lasers are the most powerful sources of X-ray radiation. They constitute invaluable tools for a broad range of research 1 ; however, their dependence on largescale radiofrequency electron accelerators means that only a few of these sources exist worldwide. Laser-driven plasmawave accelerators 2-10 provide markedly increased accelerating fields and hence offer the potential to shrink the size and cost of these X-ray sources to the university-laboratory scale. Here, we demonstrate the generation of soft-X-ray undulator radiation with laser-plasma-accelerated electron beams. The well-collimated beams deliver soft-X-ray pulses with an expected pulse duration of ∼10 fs (inferred from plasma-accelerator physics). Our source draws on a 30-cmlong undulator 11 and a 1.5-cm-long accelerator delivering stable electron beams 10 with energies of ∼210 MeV. The spectrum of the generated undulator radiation typically consists of a main peak centred at a wavelength of ∼18 nm (fundamental), a second peak near ∼9 nm (second harmonic) and a highenergy cutoff at ∼7 nm. Magnetic quadrupole lenses 11 ensure efficient electron-beam transport and demonstrate an enabling technology for reproducible generation of tunable undulator radiation. The source is scalable to shorter wavelengths by increasing the electron energy. Our results open the prospect of tunable, brilliant, ultrashort-pulsed X-ray sources for small-scale laboratories.Resolving the structure and dynamics of matter on the atomic scale requires a probe with ångstrøm resolution in space and femtosecond to attosecond resolution in time. Third-generation synchrotron sources produce X-ray pulses with durations of typically a few tens of picoseconds and can achieve 100 fs by using complex beam-manipulation techniques 12,13 . They have already proven their capability of imaging static structures with atomic (spatial) resolution 1 and upcoming X-ray free-electron lasers hold promise for also extending the temporal resolution into the atomic/sub-atomic range [14][15][16][17][18] . Both of these sources consist of an electron accelerator and an undulator, which is a periodic magnetic structure that forces the electrons to oscillate and emit radiation 19 . Whereas current facilities require a kilometre-scale accelerator, new laser-plasma accelerators offer the potential for a marked reduction in size and cost as well as pulse durations of a few femtoseconds.Femtosecond-laser-driven plasma accelerators have produced quasi-monoenergetic electron beams 2-7 with energies up to 1 GeV (refs 8, 9, 20, 21) from centimetre-scale interaction lengths. The concept is based on an ultra-intense laser pulse, which ionizes atoms of a gas target and excites a plasma wave. This trails the pulse at 1 Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany, 2 Department für Physik, Ludwig-Maximilians-Universität, Am Coulombwall 1, 85748 Garching, Germany, 3 Forschungszentrum Dresden-Rossendorf, Bautzner Landstraße 128, 01328 Dresden, Germany, 4 ...

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Section: Methodsmentioning

confidence: 99%

“…Detection of undulator radiation in some 70% of consecutive driver-laser shots indicates a remarkable reproducibility for a first proof-of-concept demonstration experiment. It can be attributed to a stable electronacceleration scheme 10 and the use of magnetic lenses 11 to guide the electron beam through the undulator.…”

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confidence: 99%

Laser-driven soft-X-ray undulator source

et al. 2009

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“…The position and length of the electron injection region depends on highly nonlinear processes such as self-focusing of the laser pulse. Thus, although stable self-injection regimes have been observed [10], large fluctuations in the acceleration length and accordingly E peak and ÁE are often experienced and the control over the bunch properties is very limited.…”

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confidence: 99%

Shock-Front Injector for High-Quality Laser-Plasma Acceleration

et al. 2013

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We report the generation of stable and tunable electron bunches with very low absolute energy spread (ÁE%5 MeV) accelerated in laser wakefields via injection and trapping at a sharp downward density jump produced by a shock front in a supersonic gas flow. The peak of the highly stable and reproducible electron energy spectrum was tuned over more than 1 order of magnitude, containing a charge of 1-100 pC and a charge per energy interval of more than 10 pC=MeV. Laser-plasma electron acceleration with Ti:sapphire lasers using this novel injection mechanism provides high-quality electron bunches tailored for applications.

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“…So far, laserbased particle acceleration schemes employ the longitudinal electric field component of a plasma wave [6][7][8] or of a tightly focused laser beam [9], but in both schemes the accelerating mode has a phase velocity that does not match the speed of light. Therefore, relativistic particles can only be accelerated over short distances and the maximum attainable energies of these devices are limited.…”

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confidence: 99%

Laser-Based Acceleration of Nonrelativistic Electrons at a Dielectric Structure

2013

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A proof-of-principle experiment demonstrating dielectric laser acceleration of non-relativistic electrons in the vicinity of a fused-silica grating is reported. The grating structure is utilized to generate an electromagnetic surface wave that travels synchronously with and efficiently imparts momentum on 28 keV electrons. We observe a maximum acceleration gradient of 25 MeV/m. We investigate in detail the parameter dependencies and find excellent agreement with numerical simulations. With the availability of compact and efficient fiber laser technology, these findings may pave the way towards an all-optical compact particle accelerator. This work also represents the demonstration of the inverse Smith-Purcell effect in the optical regime.The acceleration gradients of linear accelerators are limited by breakdown phenomena at the accelerating structures under the influence of large surface fields. Today's accelerators, which are based on metal structures driven by radio frequency fields, operate at acceleration gradients of ∼20-50 MeV/m. The upper limit in future radio frequency accelerators, such as the discussed CLIC and ILC, is ∼100 MeV/m, given by the damage threshold of the metal surfaces [1][2][3]. At optical frequencies dielectric materials withstand roughly two orders of magnitude larger field amplitudes than metals [4]. Together with the large optical field strength attainable with short laser pulses, dielectric laser accelerators (DLAs) hence may support acceleration gradients in the multi-GeV/m range [5]. With this technology lab-size accelerators, providing particle beams with energies currently only available at km-long facilities, seem feasible. Here we demonstrate the efficacy of the concept.Charged particle acceleration with oscillating fields requires an electromagnetic wave with a phase speed equal to the particle's velocity and an electric field component parallel to the particle's trajectory. So far, laserbased particle acceleration schemes employ the longitudinal electric field component of a plasma wave [6][7][8] or of a tightly focused laser beam [9], but in both schemes the accelerating mode has a phase velocity that does not match the speed of light. Therefore, relativistic particles can only be accelerated over short distances and the maximum attainable energies of these devices are limited. Exploiting the near-field of periodic structures, for example of optical gratings, offers the possibility to continuously accelerate non-relativistic as well as relativistic particles. In essence, the effect of the grating is to rectify the oscillating field in the frame co-moving with the electron, conceptually similar to conventional radio frequency devices. Single gratings can only be used to accelerate non-relativistic electrons, an effect also known as the inverse Smith-Purcell effect [10][11][12]. However, double grating structures, in which electrons propagate in a channel between two gratings facing each other, support a longitudinal, accelerating speed-of-light eigenmode that can be used to a...

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Generation of Stable, Low-Divergence Electron Beams by Laser-Wakefield Acceleration in a Steady-State-Flow Gas Cell

Cited by 210 publications

References 25 publications

Laser-driven soft-X-ray undulator source

Laser-driven soft-X-ray undulator source

Shock-Front Injector for High-Quality Laser-Plasma Acceleration

Laser-Based Acceleration of Nonrelativistic Electrons at a Dielectric Structure

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