| 1. |
- Klementiev, K., et al.
(författare)
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High performance emission spectrometer at Balder/MAX IV beamline
- 2016
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 712:1
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Tidskriftsartikel (refereegranskat)abstract
- The emission spectrometer at Balder/MAX IV beamline is presented. Its unique features are described. Comparison is given with other types of curved crystals analyzers.
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| 2. |
- Klementiev, K., et al.
(författare)
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The BALDER Beamline at the MAX IV Laboratory
- 2016
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 712:1
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption spectroscopy (XAS) includes well-established methods to study the local structure around the absorbing element - extended X-ray absorption fine structure (EXAFS), and the effective oxidation number or to quantitatively determine the speciation of an element in a complex matrix - X-ray absorption near-edge structure (XANES). The increased brilliance and intensities available at the new generation of synchrotron light sources makes it possible to study, in-situ and in-operando, much more dilute systems with relevance for natural systems, as well as the micro-scale variability and dynamics of chemical reactions on the millisecond time-scale. The design of the BALDER beamline at the MAX IV Laboratory 3 GeV ring has focused on a high flux of photons in a wide energy range, 2.4-40 keV, where the K-edge is covered for the elements S to La, and the L 3-edge for all elements heavier than Sb. The overall design of the beamline will allow large flexibility in energy range, beam size and data collection time. The other focus of the beamline design is the possibility to perform multi-technique analyses on samples. Development of sample environment requires focus on implementation of auxiliary methods in such a way that techniques like Fourier transform infrared (FTIR) spectroscopy, UV-Raman spectroscopy, X-ray diffraction and/or mass spectrometry can be performed simultaneously as the XAS study. It will be a flexible system where different instruments can be plugged in and out depending on the needs for the particular investigation. Many research areas will benefit from the properties of the wiggler based light source and the capabilities to perform in-situ and in-operando measurements, for example environmental and geochemical sciences, nuclear chemistry, catalysis, materials sciences, and cultural heritage.
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| 3. |
- Simonelli, L., et al.
(författare)
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The CLEAR X-ray emission spectrometer available at the CLAESS beamline of ALBA synchrotron
- 2023
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Ingår i: Journal of Synchrotron Radiation. - 0909-0495. ; 30, s. 235-241
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Tidskriftsartikel (refereegranskat)abstract
- The CLEAR X-ray emission spectrometer installed at the CLAESS beamline of the ALBA synchrotron is described. It is an energy-dispersive spectrometer based on Rowland circle geometry with 1 m-diameter circle. The energy dispersion is achieved by the combination of a diced analyzer crystal and a unidimensional detector. A single unconventional dynamically bent analyzer crystal (Si 111) permits a wide energy range to be covered, just by exploiting its different reflections (333, 444, 555, 777, 888): 6-22 keV, with a spectrometer efficiency that decreases above 11 keV because of the Si detector thickness (Mythen, 350 μm), while the relative scattering intensities for the Si 333, 444, 555, 777 and 888 reflections correspond to 36, 40, 21, 13 and 15, respectively. The provided energy resolution is typically below 1-2 eV and depends on the beam size, working Bragg angle and reflection exploited. In most cases the energy dispersion ranges from 10 to 20 eV and can be enlarged by working in the out-of-Rowland geometry up to 40 eV. The spectrometer works in full backscattering geometry with the beam passing through the two halves of the analyzer. The vacuum beam path and the particular geometry allow a typical average noise of only 0.5 counts per second per pixel. The spectrometer is mainly used for measuring emission lines and high-resolution absorption spectra, with a typical scanning time for highly concentrated systems of around half an hour, including several repeats. The intrinsic energy dispersion allows systematic collection of resonant X-ray emission maps by measuring high-resolution absorption spectra. Moreover, it allows spectra to be measured on a single-shot basis. Resonant inelastic X-ray scattering experiments to probe electronic excitations are feasible, although the spectrometer is not optimized for this purpose due to the limited energy resolution and scattering geometry provided. In that case, to minimize the quasi-elastic line, the spectrometer is able to rotate along the beam path. Advantages and disadvantages with respect to other existing spectrometers are highlighted.
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| 4. |
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| 5. |
- Klementiev, K., et al.
(författare)
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XAFSmass : A program for calculating the optimal mass of XAFS samples
- 2016
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 712:1
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Tidskriftsartikel (refereegranskat)abstract
- We present a new implementation of the XAFSmass program that calculates the optimal mass of XAFS samples. It has several improvements as compared to the old Windows based program XAFSmass: 1) it is truly platform independent, as provided by Python language, 2) it has an improved parser of chemical formulas that enables parentheses and nested inclusion-to-matrix weight percentages. The program calculates the absorption edge height given the total optical thickness, operates with differently determined sample amounts (mass, pressure, density or sample area) depending on the aggregate state of the sample and solves the inverse problem of finding the elemental composition given the experimental absorption edge jump and the chemical formula.
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| 6. |
- Manzanillas, L., et al.
(författare)
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Development of multi-element monolithic germanium detectors for X-ray detection at synchrotron facilities
- 2023
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 1047
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Tidskriftsartikel (refereegranskat)abstract
- In past years efforts have concentrated on the development of arrays of Silicon Drift Detectors for X-ray spectroscopy. This is in stark contrast to the little effort that has been devoted to the improvement of germanium detectors, in particular for synchrotron applications. Germanium detectors have better energy resolution and are more efficient in detecting high energy photons than silicon detectors. In this context, the detector consortium of the European project LEAPS-INNOV has set an ambitious R&D program devoted to the development of a new generation of multi-element monolithic germanium detectors for X-ray detection. In order to improve the performance of the detector under development, simulations of the different detector design options have been performed. In this contribution, the efforts in terms of R&D are outlined with a focus on the modelization of the detector geometry and first performance results. These performance results show that a signal-to-background ratio larger than 1000 can be achieved in the energy range of interest from 5 keV to 100 keV.
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| 7. |
- Orsini, F., et al.
(författare)
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XAFS-DET : A new high throughout X-ray spectroscopy detector system developed for synchrotron applications
- 2023
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 1045
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Tidskriftsartikel (refereegranskat)abstract
- The high brilliance and coherent beams resulting from recent upgraded synchrotron radiation facilities open the way for a large range of experiments, where detectors play a key role in the techniques and methods developed to fully exploit the upgraded synchrotron. For instance, one of the major limitations of XAFS experiment is the performance of the detectors. In order to be able to measure more challenging samples and to cope with the very high photon flux of the current and future (diffraction limited) sources, technological developments of detectors are necessary. In this framework, the germanium detector developed in the European project LEAPS-INNOV aims at improving several technological aspects. This type of detector represents a very important class of instruments for X-ray spectroscopy due to the fact that they enable to detect efficiently photons of considerable higher energy with respect to silicon detectors. The objective of this project consists in pushing the detector performance beyond the state-of-the-art. Preliminary layout and main choices for the design studies of this new detector are presented in this paper.
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| 8. |
- Purans, J., et al.
(författare)
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Local electronic structure rearrangements and strong anharmonicity in YH3 under pressures up to 180 GPa
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The discovery of superconductivity above 250 K at high pressure in LaH10 and the prediction of overcoming the room temperature threshold for superconductivity in YH10 urge for a better understanding of hydrogen interaction mechanisms with the heavy atom sublattice in metal hydrides under high pressure at the atomic scale. Here we use locally sensitive X-ray absorption fine structure spectroscopy (XAFS) to get insight into the nature of phase transitions and the rearrangements of local electronic and crystal structure in archetypal metal hydride YH3 under pressure up to 180 GPa. The combination of the experimental methods allowed us to implement a multiscale length study of YH3: XAFS (short-range), Raman scattering (medium-range) and XRD (long-range). XANES data evidence a strong effect of hydrogen on the density of 4d yttrium states that increases with pressure and EXAFS data evidence a strong anharmonicity, manifested as yttrium atom vibrations in a double-well potential.
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| 9. |
- Rogström, Lina, 1983-, et al.
(författare)
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Structural changes in Ti1-xAlxN coatings during turning : A XANES and EXAFS study of worn tools
- 2023
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 612
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Tidskriftsartikel (refereegranskat)abstract
- Structural changes in Ti1-xAlxN coated tool inserts used for turning in 316L stainless steel were investigated by XANES, EXAFS, EDS, and STEM. For coarse-grained fcc-structured Ti1-xAlxN coatings, with 0 ≤ x ≤ 0.62, the XANES spectrum changes with Al-content. XANES Ti 1s line-scans across the rake face of the worn samples reveals that TiN-enriched domains have formed during turning in Ti0.47Al0.53N and Ti0.38Al0.62N samples as a result of spinodal decomposition. The XANES spectra reveal the locations on the tool in which the most TiN-rich domains have formed, indicating which part of the tool-chip contact area that experienced the highest temperature during turning. Changes in the pre-edge features in the XANES spectra reveal that structural changes occur also in the w-TiAlN phase in fine-grained Ti0.38Al0.62N during turning. EDS shows that Cr and Fe from the steel adhere to the tool rake face during machining. Cr 1s and Fe 1s XANES show that Cr is oxidized in the end of the contact length while the adhered Fe retains in the same fcc-structure as that of the 316L stainless steel.
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| 10. |
- Salamatin, D. A., et al.
(författare)
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The new high-pressure hexagonal Laves phase of the YbZn2 compound
- 2023
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388. ; 946
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Tidskriftsartikel (refereegranskat)abstract
- The new metastable high-pressure high-temperature synthesized hexagonal Laves phase compound YbZn2 was investigated. The unit cell parameters, low-temperature Sommerfeld coefficient and Debye temperature were determined. X-ray absorption studies and calculations based on dynamical mean-field theory (DMFT) showed the intermediate valence behavior of YbZn2 with mean Yb valence about 2.55. The values of hyperfine electric parameters in Zn (6h) sites were determined by means of 111Cd-time differential perturbed angular correlations and theoretical density functional calculations. DMFT calculations showed that the main contribution to the electron density of states at the Fermi level is due to Yb 4f electrons, while Zn spd electrons lie much lower in energy.
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