High energy resolution five-crystal spectrometer for high quality fluorescence and absorption measurements on an x-ray absorption spectroscopy beamline

Abstract

Fluorescence detection is classically achieved with a solid state detector (SSD) on x-ray absorption spectroscopy (XAS) beamlines. This kind of detection however presents some limitations related to the limited energy resolution and saturation. Crystal analyzer spectrometers (CAS) based on a Johann-type geometry have been developed to overcome these limitations. We have tested and installed such a system on the BM30B/CRG-FAME XAS beamline at the ESRF dedicated to the structural investigation of very dilute systems in environmental, material and biological sciences. The spectrometer has been designed to be a mobile device for easy integration in multi-purpose hard x-ray synchrotron beamlines or even with a laboratory x-ray source. The CAS allows to collect x-ray photons from a large solid angle with five spherically bent crystals. It will cover a large energy range allowing to probe fluorescence lines characteristic of all the elements from Ca (Z = 20) to U (Z = 92). It provides an energy resolution of 1-2 eV. XAS spectroscopy is the main application of this device even if other spectroscopic techniques (RIXS, XES, XRS, etc.) can be also achieved with it. The performances of the CAS are illustrated by two experiments that are difficult or impossible to perform with SSD and the complementarity of the CAS vs SSD detectors is discussed.

In situ site-selective transition metal K-edge XAS: a powerful probe of the transformation of mixed-valence compounds

“…25 The energy of the incident radiation was selected using a pair of Si(220) crystals (flux of ca. 5.10 11 photons.s --1 ).…”

Characterization of Germanium Speciation in Sphalerite (ZnS) from Central and Eastern Tennessee, USA, by X-ray Absorption Spectroscopy

“…Finally, a feedback system was used to maximize the output of the two-crystal X-ray monochromator. Fluorescence detection was achieved using two spherically bent crystal analysers (Si660, 1 m bending radius) in Johann-type geometry [31,32]. A silicon drift detector (Vortex) was used for the detection of the signal reflected by the two analysers.…”

X-ray absorption spectroscopy investigations on radioactive matter using MARS beamline at SOLEIL synchrotron

“…Total energy resolution is then limited to the intrinsic resolution of the analyzer, the energy spreading due to the Johann's geometry being minimum, the incident photon bandwidth (due to the monochromator) and the vertical size of the beam on the sample. The total energy resolution has been measured to 2.2 eV, quite far from the theoretical expected value probably due to microstrains in the silicon bent wafer as it has been already observed on bent crystal with the same radius of curvature [20].…”

“…Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 6/1/15 1:15 PM The spectrometer is a 4-crystal spectrometer adapted from the 5-crystal one installed on BM30B/CRG-FAME beamline at the ESRF [19,20]. The lower number of crystals was required because of the limited place around (KB system and in some case shielding around the sample) ( Figure 6).…”