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- ItemXUV double-pulses with femtosecond to 650 ps separation from a multilayer-mirror-based split-and-delay unit at FLASH(Chester : IUCr, 2018-8-3) Sauppe, Mario; Rompotis, Dimitrios; Erk, Benjamin; Bari, Sadia; Bischoff, Tobias; Boll, Rebecca; Bomme, Cédric; Bostedt, Christoph; Dörner, Simon; Düsterer, Stefan; Feigl, Torsten; Flückiger, Leonie; Gorkhover, Tais; Kolatzki, Katharina; Langbehn, Bruno; Monserud, Nils; Müller, Erland; Müller, Jan P.; Passow, Christopher; Ramm, Daniel; Rolles, Daniel; Schubert, Kaja; Schwob, Lucas; Senfftleben, Björn; Treusch, Rolf; Ulmer, Anatoli; Weigelt, Holger; Zimbalski, Jannis; Zimmermann, Julian; Möller, Thomas; Rupp, DanielaExtreme ultraviolet (XUV) and X-ray free-electron lasers enable new scientific opportunities. Their ultra-intense coherent femtosecond pulses give unprecedented access to the structure of undepositable nanoscale objects and to transient states of highly excited matter. In order to probe the ultrafast complex light-induced dynamics on the relevant time scales, the multi-purpose end-station CAMP at the free-electron laser FLASH has been complemented by the novel multilayer-mirror-based split-and-delay unit DESC (DElay Stage for CAMP) for time-resolved experiments. XUV double-pulses with delays adjustable from zero femtoseconds up to 650 picoseconds are generated by reflecting under near-normal incidence, exceeding the time range accessible with existing XUV split-and-delay units. Procedures to establish temporal and spatial overlap of the two pulses in CAMP are presented, with emphasis on the optimization of the spatial overlap at long time-delays via time-dependent features, for example in ion spectra of atomic clusters.
- ItemThe 1-Megapixel pnCCD detector for the Small Quantum Systems Instrument at the European XFEL: system and operation aspects(Chester : IUCr, 2021) Kuster, Markus; Ahmed, Karim; Ballak, Kai Erik; Danilevski, Cyril; Ekmedžić, Marko; Fernandes, Bruno; Gessler, Patrick; Hartmann, Robert; Hauf, Steffen; Holl, Peter; Meyer, Michael; Montaño, Jacobo; Münnich, Astrid; Ovcharenko, Yevheniy; Rennhack, Nils; Rüter, Tonn; Rupp, Daniela; Schlosser, Dieter; Setoodehnia, Kiana; Schmitt, Rüdiger; Strüder, Lothar; Tanyag, Rico Mayro P.; Ulmer, Anatoli; Yousef, HazemThe X-ray free-electron lasers that became available during the last decade, like the European XFEL (EuXFEL), place high demands on their instrumentation. Especially at low photon energies below 1 keV, detectors with high sensitivity, and consequently low noise and high quantum efficiency, are required to enable facility users to fully exploit the scientific potential of the photon source. A 1-Megapixel pnCCD detector with a 1024 × 1024 pixel format has been installed and commissioned for imaging applications at the Nano-Sized Quantum System (NQS) station of the Small Quantum System (SQS) instrument at EuXFEL. The instrument is currently operating in the energy range between 0.5 and 3 keV and the NQS station is designed for investigations of the interaction of intense FEL pulses with clusters, nano-particles and small bio-molecules, by combining photo-ion and photo-electron spectroscopy with coherent diffraction imaging techniques. The core of the imaging detector is a pn-type charge coupled device (pnCCD) with a pixel pitch of 75 µm × 75 µm. Depending on the experimental scenario, the pnCCD enables imaging of single photons thanks to its very low electronic noise of 3 e− and high quantum efficiency. Here an overview on the EuXFEL pnCCD detector and the results from the commissioning and first user operation at the SQS experiment in June 2019 are presented. The detailed descriptions of the detector design and capabilities, its implementation at EuXFEL both mechanically and from the controls side as well as important data correction steps aim to provide useful background for users planning and analyzing experiments at EuXFEL and may serve as a benchmark for comparing and planning future endstations at other FELs.
- ItemCAMP@FLASH: an end-station for imaging, electron- and ion-spectroscopy, and pump–probe experiments at the FLASH free-electron laser(Chester : IUCr, 2018-8-2) Erk, Benjamin; Müller, Jan P.; Bomme, Cédric; Boll, Rebecca; Brenner, Günter; Chapman, Henry N.; Correa, Jonathan; Düsterer, Stefan; Dziarzhytski, Siarhei; Eisebitt, Stefan; Graafsma, Heinz; Grunewald, Sören; Gumprecht, Lars; Hartmann, Robert; Hauser, Günter; Keitel, Barbara; von Korff Schmising, Clemens; Kuhlmann, Marion; Manschwetus, Bastian; Mercadier, Laurent; Müller, Erland; Passow, Christopher; Plönjes, Elke; Ramm, Daniel; Rompotis, Dimitrios; Rudenko, Artem; Rupp, Daniela; Sauppe, Mario; Siewert, Frank; Schlosser, Dieter; Strüder, Lothar; Swiderski, Angad; Techert, Simone; Tiedtke, Kai; Tilp, Thomas; Treusch, Rolf; Schlichting, Ilme; Ullrich, Joachim; Moshammer, Robert; Möller, Thomas; Rolles, DanielThe non-monochromatic beamline BL1 at the FLASH free-electron laser facility at DESY was upgraded with new transport and focusing optics, and a new permanent end-station, CAMP, was installed. This multi-purpose instrument is optimized for electron- and ion-spectroscopy, imaging and pump–probe experiments at free-electron lasers. It can be equipped with various electron- and ion-spectrometers, along with large-area single-photon-counting pnCCD X-ray detectors, thus enabling a wide range of experiments from atomic, molecular, and cluster physics to material and energy science, chemistry and biology. Here, an overview of the layout, the beam transport and focusing capabilities, and the experimental possibilities of this new end-station are presented, as well as results from its commissioning.
- ItemDeep neural networks for classifying complex features in diffraction images(Woodbury, NY : Inst., 2019) Zimmermann, Julian; Langbehn, Bruno; Cucini, Riccardo; Di Fraia, Michele; Finetti, Paola; LaForge, Aaron C.; Nishiyama, Toshiyuki; Ovcharenko, Yevheniy; Piseri, Paolo; Plekan, Oksana; Prince, Kevin C.; Stienkemeier, Frank; Ueda, Kiyoshi; Callegari, Carlo; Möller, Thomas; Rupp, DanielaIntense short-wavelength pulses from free-electron lasers and high-harmonic-generation sources enable diffractive imaging of individual nanosized objects with a single x-ray laser shot. The enormous data sets with up to several million diffraction patterns present a severe problem for data analysis because of the high dimensionality of imaging data. Feature recognition and selection is a crucial step to reduce the dimensionality. Usually, custom-made algorithms are developed at a considerable effort to approximate the particular features connected to an individual specimen, but because they face different experimental conditions, these approaches do not generalize well. On the other hand, deep neural networks are the principal instrument for today's revolution in automated image recognition, a development that has not been adapted to its full potential for data analysis in science. We recently published [Langbehn et al., Phys. Rev. Lett. 121, 255301 (2018)] the application of a deep neural network as a feature extractor for wide-angle diffraction images of helium nanodroplets. Here we present the setup, our modifications, and the training process of the deep neural network for diffraction image classification and its systematic bench marking. We find that deep neural networks significantly outperform previous attempts for sorting and classifying complex diffraction patterns and are a significant improvement for the much-needed assistance during postprocessing of large amounts of experimental coherent diffraction imaging data.
- ItemPublisher Correction: Coherent diffractive imaging of single helium nanodroplets with a high harmonic generation source (Nature communications (2017) 8 1 (493))([London] : Nature Publishing Group UK, 2018) Rupp, Daniela; Monserud, Nils; Langbehn, Bruno; Sauppe, Mario; Zimmermann, Julian; Ovcharenko, Yevheniy; Möller, Thomas; Frassetto, Fabio; Poletto, Luca; Trabattoni, Andrea; Calegari, Francesca; Nisoli, Mauro; Sander, Katharina; Peltz, Christian; Vrakking, Marc J.; Fennel, Thomas; Rouzée, ArnaudIn the original version of this Article, the affiliation for Luca Poletto was incorrectly given as 'European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Hamburg, Germany', instead of the correct 'CNR, Istituto di Fotonica e Nanotecnologie Padova, Via Trasea 7, 35131 Padova, Italy'. This has now been corrected in both the PDF and HTML versions of the Article.
- ItemFinding the semantic similarity in single-particle diffraction images using self-supervised contrastive projection learning(London : Nature Publ. Group, 2023) Zimmermann, Julian; Beguet, Fabien; Guthruf, Daniel; Langbehn, Bruno; Rupp, DanielaSingle-shot coherent diffraction imaging of isolated nanosized particles has seen remarkable success in recent years, yielding in-situ measurements with ultra-high spatial and temporal resolution. The progress of high-repetition-rate sources for intense X-ray pulses has further enabled recording datasets containing millions of diffraction images, which are needed for the structure determination of specimens with greater structural variety and dynamic experiments. The size of the datasets, however, represents a monumental problem for their analysis. Here, we present an automatized approach for finding semantic similarities in coherent diffraction images without relying on human expert labeling. By introducing the concept of projection learning, we extend self-supervised contrastive learning to the context of coherent diffraction imaging and achieve a dimensionality reduction producing semantically meaningful embeddings that align with physical intuition. The method yields substantial improvements compared to previous approaches, paving the way toward real-time and large-scale analysis of coherent diffraction experiments at X-ray free-electron lasers.
- ItemThin-disk laser-pumped OPCPA system delivering 4.4 TW few-cycle pulses(Washington, DC : Soc., 2020) Kretschmar, Martin; Tuemmler, Johannes; Schütte, Bernd; Hoffmann, Andreas; Senfftleben, Björn; Mero, Mark; Sauppe, Mario; Rupp, Daniela; Vrakking, Marc J.J.; Will, Ingo; Nagy, TamasWe present an optical parametric chirped pulse amplification (OPCPA) system delivering 4.4 TW pulses centered at 810 nm with a sub-9 fs duration and a carrier-envelope phase stability of 350 mrad. The OPCPA setup pumped by sub-10 ps pulses from two Yb:YAG thin-disk lasers at 100 Hz repetition rate is optimized for a high conversion-efficiency. The terawatt pulses of the OPCPA are utilized for generating intense extreme ultraviolet (XUV) pulses by high-order harmonic generation, achieving XUV pulse energies approaching the microjoule level. © 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
- ItemCoherent diffractive imaging of single helium nanodroplets with a high harmonic generation source([London] : Nature Publishing Group UK, 2017) Rupp, Daniela; Monserud, Nils; Langbehn, Bruno; Sauppe, Mario; Zimmermann, Julian; Ovcharenko, Yevheniy; Möller, Thomas; Frassetto, Fabio; Poletto, Luca; Trabattoni, Andrea; Calegari, Francesca; Nisoli, Mauro; Sander, Katharina; Peltz, Christian; J. Vrakking, Marc; Fennel, Thomas; Rouzée, ArnaudCoherent diffractive imaging of individual free nanoparticles has opened routes for the in situ analysis of their transient structural, optical, and electronic properties. So far, single-shot single-particle diffraction was assumed to be feasible only at extreme ultraviolet and X-ray free-electron lasers, restricting this research field to large-scale facilities. Here we demonstrate single-shot imaging of isolated helium nanodroplets using extreme ultraviolet pulses from a femtosecond-laser-driven high harmonic source. We obtain bright wide-Angle scattering patterns, that allow us to uniquely identify hitherto unresolved prolate shapes of superfluid helium droplets. Our results mark the advent of single-shot gas-phase nanoscopy with lab-based short-wavelength pulses and pave the way to ultrafast coherent diffractive imaging with phase-controlled multicolor fields and attosecond pulses.
- ItemThree-Dimensional Shapes of Spinning Helium Nanodroplets(College Park, Md. : APS, 2018) Langbehn, Bruno; Sander, Katharina; Ovcharenko, Yevheniy; Peltz, Christian; Clark, Andrew; Coreno, Marcello; Cucini, Riccardo; Drabbels, Marcel; Finetti, Paola; Di Fraia, Michele; Giannessi, Luca; Grazioli, Cesare; Iablonskyi, Denys; LaForge, Aaron C.; Nishiyama, Toshiyuki; Oliver Álvarez de Lara, Verónica; Piseri, Paolo; Plekan, Oksana; Ueda, Kiyoshi; Zimmermann, Julian; Prince, Kevin C.; Stienkemeier, Frank; Callegari, Carlo; Fennel, Thomas; Rupp, Daniela; Möller, ThomasA significant fraction of superfluid helium nanodroplets produced in a free-jet expansion has been observed to gain high angular momentum resulting in large centrifugal deformation. We measured single-shot diffraction patterns of individual rotating helium nanodroplets up to large scattering angles using intense extreme ultraviolet light pulses from the FERMI free-electron laser. Distinct asymmetric features in the wide-angle diffraction patterns enable the unique and systematic identification of the three-dimensional droplet shapes. The analysis of a large data set allows us to follow the evolution from axisymmetric oblate to triaxial prolate and two-lobed droplets. We find that the shapes of spinning superfluid helium droplets exhibit the same stages as classical rotating droplets while the previously reported metastable, oblate shapes of quantum droplets are not observed. Our three-dimensional analysis represents a valuable landmark for clarifying the interrelation between morphology and superfluidity on the nanometer scale.
- ItemImaging plasma formation in isolated nanoparticles with ultrafast resonant scattering(Melville, NY : AIP Publishing LLC, 2020) Rupp, Daniela; Flückiger, Leonie; Adolph, Marcus; Colombo, Alessandro; Gorkhover, Tais; Harmand, Marion; Krikunova, Maria; Müller, Jan Philippe; Oelze, Tim; Ovcharenko, Yevheniy; Richter, Maria; Sauppe, Mario; Schorb, Sebastian; Treusch, Rolf; Wolter, David; Bostedt, Christoph; Möller, ThomasWe have recorded the diffraction patterns from individual xenon clusters irradiated with intense extreme ultraviolet pulses to investigate the influence of light-induced electronic changes on the scattering response. The clusters were irradiated with short wavelength pulses in the wavelength regime of different 4d inner-shell resonances of neutral and ionic xenon, resulting in distinctly different optical properties from areas in the clusters with lower or higher charge states. The data show the emergence of a transient structure with a spatial extension of tens of nanometers within the otherwise homogeneous sample. Simulations indicate that ionization and nanoplasma formation result in a light-induced outer shell in the cluster with a strongly altered refractive index. The presented resonant scattering approach enables imaging of ultrafast electron dynamics on their natural timescale.