The CLEAR X-ray emission spectrometer available at the CLAESS beamline of ALBA synchrotron

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.

Temperature dependent local inhomogeneity and magnetic moments of (Li1−xFex)OHFeSe superconductors

“…The measurements were performed studying Fe Kedge (7.11 keV) absorption spectra between the temperature 10 and 290 K in the transmission mode with the polarisation of the incident beam parallel to the ab plane. Fe Kb XES measurements were carried out using a CLEAR spectrometer 49,50 that is based on a diced Si(333) dynamically bent analyzer crystal and a positionsensitive Mythen detector. The data on the Fe Kb lines were acquired by exciting the sample well above the Fe K-edge, with a total energy resolution of B0.9 eV.…”

Mercury speciation in selenium enriched wheat plants exposed to mercury pollution

“…Conventional XAS measurements were performed in uorescence mode at liquid nitrogen temperature using a multi-element silicon drift detector with Xspress3 electronics. High energy resolution Hg L 3 -edge XANES (HERFD) spectra were collected using the CLEAR spectrometer available at the beamline based on Johansson-like dynamical-bent diced-analyser Si crystals for scanning-free energy dispersive acquisition (Simonelli et al 2023). The Hg Lα 1 emission was collected using the Si(444) re ection of the analysers working in backscattering geometry.…”

Effects of A -site ordering on the Mn local structure and polar phases of RBaMn2O6 ( Subı́as1, Blasco2, Cuartero3 et al. 2023Phys. Rev. BSelf Cite3000View full textAdd to dashboardCite

“…HERFD-XAS measurements at the Mn K edge were performed at the CLAESS beamline [23] of the ALBA Synchrotron (Cerdanyola del Vallès, Spain) using a Si (311) double-crystal monochromator. HERFD-XAS spectra were collected in backscattering geometry at the maximum of the Mn Kβ 1,3 (6490 eV) emission line using the CLEAR spectrometer [24]. The overall energy resolution was determined to be 0.5 eV from the full width at half maximum of the quasielastic peak collected from a Kapton tape.…”