Compression of Subrelativistic Space-Charge-Dominated Electron Bunches for Single-Shot Femtosecond Electron Diffraction

Oudheusden, T. van; Pasmans, P.L.E.M.; Geer, S.B. van der; Loos, M. J. de; Wiel, M.J. van der; Luiten, O.J.

doi:10.1103/physrevlett.105.264801

Cited by 304 publications

(283 citation statements)

References 18 publications

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“…High-brightness electron beams for UED are typically generated from photocathodes [5][6][7][8] . The comparatively small inherent transverse coherence length of such sources is effectively increased by beam expansion with propagation and a beam aperture, according to the van CittertZernike theorem 9 .…”

mentioning

confidence: 99%

“…With femtosecond excitation, the initial electron pulse duration is limited by the spatial extent of the overlap of the cold atoms and the two laser pulses, corresponding to around 150 ps for our apparatus (see Methods). Although that pulse duration is already short enough to observe the structural dynamics of a myoglobin mutant protein 4 , it may be possible to reduce the bunch length by up to three orders of magnitude using recently demonstrated radio frequency compression techniques 7,15,16 .…”

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High-coherence picosecond electron bunches from cold atoms

et al. 2013

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Ultrafast electron diffraction enables the study of molecular structural dynamics with atomic resolution at subpicosecond timescales, with applications in solid-state physics and rational drug design. Progress with ultrafast electron diffraction has been constrained by the limited transverse coherence of high-current electron sources. Photoionization of laser-cooled atoms can produce electrons of intrinsically high coherence, but has been too slow for ultrafast electron diffraction. Ionization with femtosecond lasers should in principle reduce the electron pulse duration, but the high bandwidth inherent to short laser pulses is expected to destroy the transverse coherence. Here we demonstrate that a two-colour process with femtosecond excitation followed by nanosecond photoionization can produce picosecond electron bunches with high transverse coherence. Ultimately, the unique combination of ultrafast ionization, high coherence and three-dimensional bunch shaping capabilities of cold atom electron sources have the potential for realising the brightness and coherence requirements for single-shot electron diffraction from crystalline biological samples.

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High-coherence picosecond electron bunches from cold atoms

et al. 2013

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“…The energy spread causes degradation in temporal resolution by the lengthening of the electron bunches. This effect can be cancelled by compressing the electron pulses using established RF techniques [9,10]. The ultimate temporal resolution is governed by the longitudinal emittance which is determined by the uncorrelated pulse length and energy spread.…”

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confidence: 99%

Energy spread of ultracold electron bunches extracted from a laser cooled gas

Franssen

Kromwijk

Vredenbregt

et al. 2018

J. Phys. B: At. Mol. Opt. Phys.

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Abstract.Ultrashort and ultracold electron bunches created by near-threshold femtosecond photoionization of a laser-cooled gas hold great promise for single-shot ultrafast diffraction experiments. In previous publications the transverse beam quality and the bunch length have been determined. Here the longitudinal energy spread of the generated bunches is measured for the first time, using a specially developed Wien filter. The Wien filter has been calibrated by determining the average deflection of the electron bunch as a function of magnetic field. The measured relative energy spread σ U U = 0.64 ± 0.09% agrees well with the theoretical model which states that it is governed by the width of the ionization laser and the acceleration length.

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“…Here, electrons were created from metallic surfaces by short laser pulses and accelerated in dc electric fields [7,8], yielding sub-picosecond electron pulses of moderate coherence and brilliance. Radio-frequency cavities allow for temporal compression of electron pulses through phase-space rotation, shortening the pulse duration to below 100 fs with electron numbers of 10 6 per pulse and electron spot sizes below 100 µm [30]. Compact dc guns can achieve comparable properties by increasing the acceleration fields and reducing the path length, during which the electron pulse can expand [31][32][33][34].…”

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confidence: 99%

“…The time resolution could either be improved through a more compact design and stronger electric fields [33] or by combining the setup with an RF cavity for appropriate phase-space rotation for temporal focusing [30,31,50].…”

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Electron gun for diffraction experiments off controlled molecules

Müller¹,

Trippel²,

Długołȩcki³

et al. 2015

J. Phys. B: At. Mol. Opt. Phys.

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A dc electron gun, generating picosecond pulses with up to 8 × 10 6 electrons per pulse, was developed. Its applicability for future time-resolved-diffraction experiments on state-and conformer-selected laser-aligned or oriented gaseous samples was characterized. The focusing electrodes were arranged in a velocity-map imaging spectrometer configuration. This allowed to directly measure the spatial and velocity distributions of the electron pulses emitted from the cathode. The coherence length and pulse duration of the electron beam were characterized by these measurements combined with electron trajectory simulations. Electron diffraction data off a thin aluminum foil illustrated the coherence and resolution of the electron-gun setup.Diffractive imaging is a promising approach to unravel the microscopic details of chemical processes through the recording of so-called molecular movies in the gasphase, which trace the structural dynamics of individual molecules and nano-particles at the atomic level. Electron and x-ray diffraction are well established tools to investigate the structures of solid state samples [1], for example in transmission electron microscopy [2] or xray crystallography [3,4]. Furthermore, electron diffraction has found broad application for gas-phase structuredetermination in chemistry [5]. Recent developments have mainly focused on realizing time-resolved experiments in order to study structural dynamics, where xray and electron diffraction served as complementary approaches [6][7][8][9][10][11].To be able to record structural changes during ultrafast molecular processes of small complex molecules in the gas phase, signals from many identical molecules have to be averaged. Gas-phase investigations pose the challenge that the sample might comprise different isomers and sizes [12]. In addition, the molecules in the gas phase are typically randomly oriented. It is therefore important to provide samples, which are as clean and defined as possible, to allow for experimental averaging over multiple electron pulses. Clean molecular samples can be generated by their spatial separation according to shape [13][14][15] and size [16]. Controlling the spatial orientation of the molecules leads to an enhancement of the information that can be retrieved from a diffraction pattern, as proposed theoretically [17][18][19][20] and demonstrated experimentally for x-ray [21,22] as well as for electron diffraction [23,24]. Strong alignment or orientation is generally necessary [11,20] for three-dimensional structure reconstruction [24] and can be provided in cold supersonic molecular beams by strong-field laser alignment and mixed-field orientation [25][26][27][28][29]. The low density of these controlled gas-phase samples requires sources of large-cross-section particles or photons with large brightness, while still ensuring atomic resolution. Electron sources can meet these requirements even in table-top setups.The first sources for creating electron pulses short enough to study ultrafast processes in molecules o...

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Compression of Subrelativistic Space-Charge-Dominated Electron Bunches for Single-Shot Femtosecond Electron Diffraction

Cited by 304 publications

References 18 publications

High-coherence picosecond electron bunches from cold atoms

High-coherence picosecond electron bunches from cold atoms

Energy spread of ultracold electron bunches extracted from a laser cooled gas

Electron gun for diffraction experiments off controlled molecules

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