| 1. |
- Zhou Hagström, Nanna, 1993-, et al.
(författare)
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Megahertz-rate Ultrafast X-ray Scattering and Holographic Imaging at the European XFEL
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The advent of X-ray free-electron lasers (XFELs) has revolutionized fundamental science, from atomic to condensed matter physics, from chemistry to biology, giving researchers access to X-rays with unprecedented brightness, coherence, and pulse duration. All XFEL facilities built until recently provided X-ray pulses at a relatively low repetition rate, with limited data statistics. Here, we present the results from the first megahertz repetition rate X-ray scattering experiments at the Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL. We illustrate the experimental capabilities that the SCS instrument offers, resulting from the operation at MHz repetition rates and the availability of the novel DSSC 2D imaging detector. Time-resolved magnetic X-ray scattering and holographic imaging experiments in solid state samples were chosen as representative examples, providing an ideal test-bed for operation at megahertz rates. Nevertheless, our results are relevant and applicable to any other non-destructive XFEL experiments in the soft X-ray range.
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| 2. |
- Zhou Hagström, Nanna, 1993-, et al.
(författare)
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Megahertz-rate ultrafast X-ray scattering and holographic imaging at the European XFEL
- 2022
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Ingår i: Journal of Synchrotron Radiation. - : International Union of Crystallography (IUCr). - 0909-0495 .- 1600-5775. ; 29, s. 1454-1464
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Tidskriftsartikel (refereegranskat)abstract
- The advent of X-ray free-electron lasers (XFELs) has revolutionized fundamental science, from atomic to condensed matter physics, from chemistry to biology, giving researchers access to X-rays with unprecedented brightness, coherence and pulse duration. All XFEL facilities built until recently provided X-ray pulses at a relatively low repetition rate, with limited data statistics. Here, results from the first megahertz-repetition-rate X-ray scattering experiments at the Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL are presented. The experimental capabilities that the SCS instrument offers, resulting from the operation at megahertz repetition rates and the availability of the novel DSSC 2D imaging detector, are illustrated. Time-resolved magnetic X-ray scattering and holographic imaging experiments in solid state samples were chosen as representative, providing an ideal test-bed for operation at megahertz rates. Our results are relevant and applicable to any other non-destructive XFEL experiments in the soft X-ray range.
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| 3. |
- Asimakopoulou, Eleni Myrto, et al.
(författare)
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Development towards high-resolution kHz-speed rotation-free volumetric imaging
- 2024
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Ingår i: Optics Express. - 1094-4087. ; 32:3, s. 4413-4426
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Tidskriftsartikel (refereegranskat)abstract
- X-ray multi-projection imaging (XMPI) has the potential to provide rotation-free 3D movies of optically opaque samples. The absence of rotation enables superior imaging speed and preserves fragile sample dynamics by avoiding the centrifugal forces introduced by conventional rotary tomography. Here, we present our XMPI observations at the ID19 beamline (ESRF, France) of 3D dynamics in melted aluminum with 1000 frames per second and 8 µm resolution per projection using the full dynamical range of our detectors. Since XMPI is a method under development, we also provide different tests for the instrumentation of up to 3000 frames per second. As the high-brilliance of 4th generation light-sources becomes more available, XMPI is a promising technique for current and future X-ray imaging instruments.
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| 4. |
- Lojewski, Tobias, et al.
(författare)
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The interplay of local electron correlations and ultrafast spin dynamics in fcc Ni
- 2023
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Ingår i: Materials Research Letters. - : Taylor & Francis. - 2166-3831. ; 11:8, s. 655-661
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Tidskriftsartikel (refereegranskat)abstract
- The complex electronic structure of metallic ferromagnets is determined by a balance between exchange interaction, electron hopping leading to band formation, and local Coulomb repulsion. By combining high energy and temporal resolution in femtosecond time-resolved X-ray absorption spectroscopy with ab initio time-dependent density functional theory we analyze the electronic structure in fcc Ni on the time scale of these interactions in a pump-probe experiment. We distinguish transient broadening and energy shifts in the absorption spectra, which we demonstrate to be captured by electron repopulation respectively correlation-induced modifications of the electronic structure, requiring to take the local Coulomb interaction into account.
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| 5. |
- Reuter, Fabian, et al.
(författare)
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Laser-induced, single droplet fragmentation dynamics revealed through megahertz x-ray microscopy
- 2023
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Ingår i: Physics of Fluids. - 1070-6631. ; 35:11
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Tidskriftsartikel (refereegranskat)abstract
- The fragmentation dynamics of single water droplets from laser irradiation is studied with megahertz frame rate x-ray microscopy. Owed to the nearly refraction-free and penetrating imaging technique, we could look into the interior of the droplet and reveal that two mechanisms are responsible for the initial explosive fragmentation of the droplet. First, reflection and diffraction of the laser beam at the droplet interface result in the formation of laser ray caustics that lead to non-homogeneous heating of the droplet, locally above the critical temperature. Second, homogeneous cavitation in the droplet that is likely caused from shockwaves reflected as tension waves at the acoustic soft boundaries of the droplet. Further atomization occurs in three stages, first a fine sub-micrometer sized mist forms on the side of the droplet posterior to laser incidence, then micrometer sized droplets are expelled from the rim of an expanding liquid sheet, and finally into droplets of larger size through hole and ligament formation in the thinning liquid sheet where ligaments pinch off.
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| 6. |
- Villanueva Perez, Pablo, et al.
(författare)
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Megahertz X-ray Multi-projection imaging
- 2023
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Ingår i: arXiv.org. - 2331-8422.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- X-ray time-resolved tomography is one of the most popular X-raytechniques to probe dynamics in three dimensions (3D). Recent developments in time-resolved tomography opened the possibility of recordingkilohertz-rate 3D movies. However, tomography requires rotating thesample with respect to the X-ray beam, which prevents characterization of faster structural dynamics. Here, we present megahertz (MHz)X-ray multi-projection imaging (MHz-XMPI), a technique capable ofrecording volumetric information at MHz rates and micrometer resolution without scanning the sample. We achieved this by harnessing theunique megahertz pulse structure and intensity of the European X-rayFree-electron Laser with a combination of novel detection and reconstruction approaches that do not require sample rotations. Our approachenables generating multiple X-ray probes that simultaneously record several angular projections for each pulse in the megahertz pulse burst.We provide a proof-of-concept demonstration of the MHz-XMPI technique’s capability to probe 4D (3D+time) information on stochasticphenomena and non-reproducible processes three orders of magnitudefaster than state-of-the-art time-resolved X-ray tomography, by generating 3D movies of binary droplet collisions. We anticipate that MHz-XMPIwill enable in-situ and operando studies that were impossible before,either due to the lack of temporal resolution or because the systemswere opaque (such as for MHz imaging based on optical microscopy).
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