Measurements and Simulations of Ultralow Emittance and Ultrashort Electron Beams in the Linac Coherent Light Source

Ding, Yuantao; Brachmann, A.; Decker, F.‐J.; Dowell, D.H.; Emma, P.; Frisch, J.; Gilevich, S.; Hays, G.; Hering, Ph.; Huang, Zhirong; Iverson, R.; Loos, H.; Miahnahri, Alan; Nuhn, H.‐D.; Ratner, Daniel; Turner, Joshua J.; Welch, J.; White, William E.; Wu, Juhao

doi:10.1103/physrevlett.102.254801

Cited by 295 publications

(193 citation statements)

References 9 publications

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“…The average length of the electron bunches from which the X-ray pulses were generated was 10 fs, resulting in up to 10 fs long X-ray pulses. Simulations indicate that the duration of the photon pulse can be significantly shorter than the duration of the electron bunch 46 . Our experiment, which used non-resonant excitation, is insensitive to shot-to-shot fluctuations in X-ray pulse-frequency content.…”

Section: Methodsmentioning

confidence: 99%

Ultrafast isomerization initiated by X-ray core ionization

et al. 2015

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Rapid proton migration is a key process in hydrocarbon photochemistry. Charge migration and subsequent proton motion can mitigate radiation damage when heavier atoms absorb X-rays. If rapid enough, this can improve the fidelity of diffract-before-destroy measurements of biomolecular structure at X-ray-free electron lasers. Here we study X-ray-initiated isomerization of acetylene, a model for proton dynamics in hydrocarbons. Our time-resolved measurements capture the transient motion of protons following X-ray ionization of carbon K-shell electrons. We Coulomb-explode the molecule with a second precisely delayed X-ray pulse and then record all the fragment momenta. These snapshots at different delays are combined into a 'molecular movie' of the evolving molecule, which shows substantial proton redistribution within the first 12 fs. We conclude that significant proton motion occurs on a timescale comparable to the Auger relaxation that refills the K-shell vacancy.

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Section: Methodsmentioning

confidence: 99%

Ultrafast isomerization initiated by X-ray core ionization

et al. 2015

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“…It is, however, known that the modern FELs are operating in the self-amplified stimulated emission (SASE) mode, 68,69 which provides a temporally incoherent, spiky structure of the laser-pulse envelope. The question might arise as to how much the specific temporal profile of the laser pulse affects the results.…”

Section: Pulse Shapementioning

confidence: 99%

Nonthermal graphitization of diamond induced by a femtosecond x-ray laser pulse

2013

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Diamond irradiated with an ultrashort intense laser pulse in the regime of photon energies from soft up to hard x rays can undergo a phase transition to graphite. This transition is induced by an excitation of electrons from the valence band or from atomic deep shells of the material into its conduction band, which is followed by a transient rapid change of the interatomic potential. Such a nonthermal phase transition occurs on a femtosecond time scale, shortly after or even during the laser pulse. In this work we show that the duration of the graphitization depends on the incoming photon energy: the higher the photon energy is, the longer the secondary electron cascading which promotes the electrons into the conduction band will take. The transient kinetics of the electronic and atomic processes during the graphitization is analyzed in detail. The damage threshold fluence is calculated in the broad photon energy range and is found to be always ∼0.7 eV/atom in terms of the average dose absorbed per atom. It is confirmed that the temporal characteristics of a femtosecond laser pulse (at a fixed pulse duration and fluence) do not significantly influence the transient damage kinetics. Finally, the influence of an additional surface layer of high-Z material on the damage within diamond is discussed.

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“…Image reconstruction was carried out by phase retrieval using our iterative transform algorithm, Shrinkwrap 8 (see the Methods section). Unlike similar algorithms 7,[20][21][22][23] , Shrinkwrap solves the phase problem without requiring any a priori knowledge about the object.…”

Section: Multilayer Mirrormentioning

confidence: 99%

“…X-ray pulse lengths are measured in femtoseconds providing ultrafast shutter speeds capable of freezing individual atomic motion. Pulses of less than 60 fs are common, and pulses as short as 2 fs may be possible using very low emittance with reduced bunch charge [21]. Using this technique sub 10 fs pulses have been produced at LCLS however to date their duration has not been accurately measured.…”

Section: Introductionmentioning

confidence: 99%

“…With up to 10 13 X-ray photons per pulse [1] sufficient photons can be scattered from an isolated nanoscale object to perform coherent X-ray diffraction imaging using a single femtosecond-duration X-ray pulse [16,18]. Meanwhile the 'shutter speed' of these measurements is ultimately determined by duration of the FEL pulse: for LCLS this is 60-200 fs (and less than 10fs in ultrashort puse mode [21]). …”

Section: Introductionmentioning

confidence: 99%

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Time-resolved imaging using x-ray free electron lasers

Barty

2010

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

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The ultra-intense, ultra-short X-ray pulses provided by X-ray Free Electron Laser (XFEL) sources are ideally suited to time resolved studies of structural dynamics with spatial resolution from nanometre to atomic length scales and temporal resolution of 10 fs or less. Using coherent X-ray diffraction as a diagnostic, XFELs enable the capturing of X-ray snapshots of previously unmeasurable transient phenomena, and the study of ultrafast processes such as sample damage on the timescales which they occur. With enough photons in a single pulse to enable single-shot measurements, and short enough pulses to freeze atomic motion, researchers now have a new window into the time evolution ultrafast phenomena that are intrinsically not cyclic in nature. In this review paper we recap some of the key time-resolved imaging experiments performed at FLASH and look ahead to a new generation of experiments at higher resolution using a new generation of new XFEL sources that are only just becoming available.

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Measurements and Simulations of Ultralow Emittance and Ultrashort Electron Beams in the Linac Coherent Light Source

Cited by 295 publications

References 9 publications

Ultrafast isomerization initiated by X-ray core ionization

Ultrafast isomerization initiated by X-ray core ionization

Nonthermal graphitization of diamond induced by a femtosecond x-ray laser pulse

Time-resolved imaging using x-ray free electron lasers

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