92 research outputs found
Water Window Ptychographic Imaging with Characterized Coherent X-rays
We report on a ptychographical coherent diffractive imaging experiment in the
water window with focused soft X-rays at . An X-ray beam with
high degree of coherence was selected for ptychography at the P04 beamline of
the PETRA III synchrotron radiation source. We measured the beam coherence with
the newly developed non-redundant array method. A pinhole
in size selected the coherent part of the beam and was used for ptychographic
measurements of a lithographically manufactured test sample and fossil diatom.
The achieved resolution was for the test sample and only
limited by the size of the detector. The diatom was imaged at a resolution
better than .Comment: 22 pages. 7 figure
Photophysics of indole upon x-ray absorption
A photofragmentation study of gas-phase indole (CHN) upon
single-photon ionization at a photon energy of 420 eV is presented. Indole was
primarily inner-shell ionized at its nitrogen and carbon orbitals.
Electrons and ions were measured in coincidence by means of velocity map
imaging. The angular relationship between ionic fragments is discussed along
with the possibility to use the angle-resolved coincidence detection to perform
experiments on molecules that are strongly oriented in their recoil-frame. The
coincident measurement of electrons and ions revealed
fragmentation-pathway-dependent electron spectra, linking the structural
fragmentation dynamics to different electronic excitations. Evidence for
photoelectron-impact self-ionization was observed.Comment: 11 pages, 6 figure
On the characterization of ultra-precise VUV-focusing mirrors by means of slope measuring deflectometry
Slope measuring deflectometry allows the non-contact measuring of curves surfaces like ultra-precise elliptical cylinder shaped mirrors in use for the focusing of Synchrotron light. This paper will report on the measurement of synchrotron mirrors designed to guide and focus
Synchrotron light in the variable polarization beamline P04 at the PETRA III synchrotron at DESY (Hamburg). These mirrors were optimized by deterministic finishing technology based on topography data provided by slope measuring deflectometry. We will show the results of the mirror inspection and discuss the expected beamline performance by ray-tracing results
An endstation for resonant inelastic X-ray scattering studies of solid and liquid samples
Unsupervised real-world knowledge extraction via disentangled variational autoencoders for photon diagnostics
We present real-world data processing on measured electron time-of-flight
data via neural networks. Specifically, the use of disentangled variational
autoencoders on data from a diagnostic instrument for online wavelength
monitoring at the free electron laser FLASH in Hamburg. Without a-priori
knowledge the network is able to find representations of single-shot FEL
spectra, which have a low signal-to-noise ratio. This reveals, in a directly
human-interpretable way, crucial information about the photon properties. The
central photon energy and the intensity as well as very detector-specific
features are identified. The network is also capable of data cleaning, i.e.
denoising, as well as the removal of artefacts. In the reconstruction, this
allows for identification of signatures with very low intensity which are
hardly recognisable in the raw data. In this particular case, the network
enhances the quality of the diagnostic analysis at FLASH. However, this
unsupervised method also has the potential to improve the analysis of other
similar types of spectroscopy data
Enabling time-resolved 2D spatial-coherence measurements using the Fourier-analysis method with an integrated curved-grating beam monitor
Direct 2D spatial-coherence measurements are increasingly gaining importance at synchrotron beamlines, especially due to present and future upgrades of synchrotron facilities to diffraction-limited storage rings. We present a method to determine the 2D spatial coherence of synchrotron radiation in a direct and particularly simple way by using the Fourier-analysis method in conjunction with curved gratings. Direct photon-beam monitoring provided by a curved grating circumvents the otherwise necessary separate determination of the illuminating intensity distribution required for the Fourier-analysis method. Hence, combining these two methods allows for time-resolved spatial-coherence measurements. As a consequence, spatial-coherence degradation effects caused by beamline optics vibrations, which is one of the key issues of state-of-the-art X-ray imaging and scattering beamlines, can be identified and analyzed. © 2020 Optical Society of America
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Element-specific magnetization dynamics of complex magnetic systems probed by ultrafast magneto-optical spectroscopy
The vision to manipulate and control magnetism with light is driven on the one hand by fundamental questions of direct and indirect photon-spin interactions, and on the other hand by the necessity to cope with ever growing data volumes, requiring radically new approaches on how to write, read and process information. Here, we present two complementary experimental geometries to access the element-specific magnetization dynamics of complex magnetic systems via ultrafast magneto-optical spectroscopy in the extreme ultraviolet spectral range. First, we employ linearly polarized radiation of a free electron laser facility to demonstrate decoupled dynamics of the two sublattices of an FeGd alloy, a prerequisite for all-optical magnetization switching. Second, we use circularly polarized radiation generated in a laboratory-based high harmonic generation setup to show optical inter-site spin transfer in a CoPt alloy, a mechanism which only very recently has been predicted to mediate ultrafast metamagnetic phase transitions. © 2020 by the authors. Licensee MDPI, Basel, Switzerland
Field-free deterministic ultra fast creation of skyrmions by spin orbit torques
Magnetic skyrmions are currently the most promising option to realize
current-driven magnetic shift registers. A variety of concepts to create
skyrmions were proposed and demonstrated. However, none of the reported
experiments show controlled creation of single skyrmions using integrated
designs. Here, we demonstrate that skyrmions can be generated deterministically
on subnanosecond timescales in magnetic racetracks at artificial or natural
defects using spin orbit torque (SOT) pulses. The mechanism is largely similar
to SOT-induced switching of uniformly magnetized elements, but due to the
effect of the Dzyaloshinskii-Moriya interaction (DMI), external fields are not
required. Our observations provide a simple and reliable means for skyrmion
writing that can be readily integrated into racetrack devices
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