scholarly journals Trace-element XAFS sensitivity: a stress test for a new XRF multi-detector

2021 ◽  
Vol 28 (6) ◽  
Author(s):  
Ilaria Carlomagno ◽  
Matias Antonelli ◽  
Giuliana Aquilanti ◽  
Pierluigi Bellutti ◽  
Giuseppe Bertuccio ◽  
...  
Keyword(s):  
Trace Elements ◽  
Chemical Speciation ◽  
Stress Test ◽  
Photon Flux ◽  
Fluorescence Detector ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Counting Statistics ◽  
The Impact

X-ray absorption fine-structure (XAFS) spectroscopy can assess the chemical speciation of the elements providing their coordination and oxidation state, information generally hidden to other techniques. In the case of trace elements, achieving a good quality XAFS signal poses several challenges, as it requires high photon flux, counting statistics and detector linearity. Here, a new multi-element X-ray fluorescence detector is presented, specifically designed to probe the chemical speciation of trace 3d elements down to the p.p.m. range. The potentialities of the detector are presented through a case study: the speciation of ultra-diluted elements (Fe, Mn and Cr) in geological rocks from a calcareous formation related to the dispersal processes from Ontong (Java) volcanism (mid-Cretaceous). Trace-elements speciation is crucial in evaluating the impact of geogenic and anthropogenic harmful metals on the environment, and to evaluate the risks to human health and ecosystems. These results show that the new detector is suitable for collecting spectra of 3d elements in trace amounts in a calcareous matrix. The data quality is high enough that quantitative data analysis could be performed to determine their chemical speciation.

Chemical speciation of heterogeneously reduced Pu in synthetic brines

2006 ◽  
Vol 94 (5) ◽  
Author(s):  
Mei Ding ◽  
James L. Conca ◽  
Christophe Den Auwer ◽  
Rinat I. Gabitov ◽  
Nancy J. Hess ◽  
...  
Keyword(s):  
Fine Structure ◽  
New Mexico ◽  
Pilot Plant ◽  
Chemical Speciation ◽  
Speciation Analysis ◽  
Waste Isolation Pilot Plant ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Heterogeneous Reduction ◽  
X Ray Absorption

SummaryX-ray absorption fine structure (XAFS) spectroscopy has been used to determine the speciation of Pu precipitates prepared by the heterogeneous reduction of Pu(VI) with Al and Fe in 5 M NaCl and an ERDA-6 brine, a simulant from the Waste Isolation Pilot Plant in Carlsbad, New Mexico. NaOCl was added to some of these solutions to determine its effect on Pu speciation. Analysis of the Pu

PROXIMA 2A: A New Micro-focus Beamline for Macromolecular Crystallography

2014 ◽  
Vol 70 (a1) ◽  
pp. C1672-C1672
Author(s):  
Denis Duran ◽  
Sebastien Le Couster ◽  
Gavin Fox ◽  
Roger Fourme ◽  
Rob Meijers ◽  
...  
Keyword(s):  
High Performance ◽  
Protein Structures ◽  
Photon Flux ◽  
First Year ◽  
X Rays ◽  
Macromolecular Crystallography ◽  
Fluorescence Detector ◽  
Beam Position ◽  
X Ray ◽  
Area Detector

PROXIMA 2A is a new micro-focus and energy tunable beamline dedicated to biological macromolecular crystallography at Synchrotron SOLEIL. The beamline officially opened in March 2013, and its first year of user operation has yielded excellent results. The X-ray source is a powerful in-vacuum U24 undulator coupled to a cryo-cooled Si[111] channel-cut monochromator and a pair of focussing bimorph mirrors in Kirpatrick-Baez configuration. This combination delivers a photon flux of over 10**12 ph/s into a focal spot of 10 μm × 5 μm (H×V FWHM), which is tunable over 6 – 15 keV. The supports of the optical elements have been designed to minimise the effects of vibrations and thermal dilations on the X-ray beam position, which is stable to within 5 microns over a day. The experimental station consists of a high performance micro-diffractometer, a cryostream, an area detector (ADSC Q315r), and an X-ray fluorescence detector. The X-ray energies for MAD experiments are directly calibrated on the sample. A robot equipped with a large 9 uni-puck dewar (CATS Irelec) is available to users for the automated transfer and screening of cryo-cooled samples. The users launch their experiments via an MXCuBE interface [1], which permits the centering of the sample, collecting of diffraction images, recording of X-ray spectra and the transfer of samples. The X-ray diffraction data are of an excellent quality, and the users readily exploit the micro-focused X-rays to select the best zones of their crystals. The first year of results from users has yielded a variety of success stories including novel protein structures resolved from crystals as small as 5 microns, as well as those solved by SAD & MAD methods. The future perspectives include automated helical and grid scans, in situ plate screening and multi-crystal merging techniques.

Instantaneous Display of X-Ray Diffraction using a Diode Array Camera Tube

1968 ◽  
Vol 12 ◽  
pp. 165-173 ◽  
Author(s):  
Arthur N. Chester ◽  
Fred B. Koch
Keyword(s):  
Low Cost ◽  
High Sensitivity ◽  
Photon Flux ◽  
Diode Array ◽  
High Quantum Efficiency ◽  
X Ray ◽  
X Ray Imaging ◽  
Counting Statistics ◽  
Electron Imaging ◽  
Array Camera

AbstractThe silicon diode array camera tube, recently developed for PICTURFPHONE® service, was modified to permit X-ray imaging. High quantum efficiency is attained without the use of a phosphor screen, since each photon absorbed in the silicon target generates several hundred hole-electron pairs for each keV of its energy, most of which can he usefully collected. The sensitivity and resolution are adequate to allow a continuous television display of the diffracted intensity as a crystal is oriented. Particular advantages of this technique include; high resolution (< 25 μm); electronically variable magnification; direct oscilloscope measurement of X-ray spot Intensity profiles and relative spot intensities because signal current is directly proportional to photon flux; high sensitivity in the range of 0.6 to 5.0 Å, potentially limited only "by counting statistics; integration times variable from < 1/60 second to minutes; and expected low cost, since the camera tube has no complicated electron imaging, and is directly interchangeable Mith a standard television vidicon. Applications which are described include crystal orientation and X-ray topography.

scholarly journals Water: Friend or Foe in Catalytic Hydrogenation? A Case Study Using Copper Catalysts

Catalysts ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 474 ◽  
Author(s):  
Alisa Govender ◽  
Abdul Mahomed ◽  
Holger Friedrich
Keyword(s):  
Copper Chromite ◽  
Supported Catalyst ◽  
Copper Catalysts ◽  
Bet Surface Area ◽  
Water Impact ◽  
X Ray Diffraction ◽  
Water Addition ◽  
X Ray ◽  
The Impact

Copper oxide supported on alumina and copper chromite were synthesized, characterized, and subsequently tested for their catalytic activity toward the hydrogenation of octanal. Thereafter, the impact of water addition on the conversion and selectivity of the catalysts were investigated. The fresh catalysts were characterized using X-ray diffraction (XRD), BET surface area and pore volume, SEM, TEM, TGA-DSC, ICP, TPR, and TPD. An initial catalytic testing study was carried out using the catalysts to optimize the temperature and the hydrogen-to-aldehyde ratio—which were found to be 160 °C and 2, respectively—to obtain the best conversion and selectivity to octanol prior to water addition. Water impact studies were carried out under the same conditions. The copper chromite catalyst showed no deactivation or change in octanol selectivity when water was added to the feed. The alumina-supported catalyst showed no change in conversion, but the octanol selectivity improved marginally when water was added.

scholarly journals Dynamic structure elucidation of chemical reactivity by laser pulses and X-ray probes

2015 ◽  
Vol 44 (14) ◽  
pp. 6313-6319 ◽  
Author(s):  
Stuart A. Bartlett ◽  
Michelle L. Hamilton ◽  
John Evans
Keyword(s):  
Chemical Speciation ◽  
Chemical Reactivity ◽  
Dynamic Structure ◽  
Laser Pulses ◽  
Chemical Transformations ◽  
Free Electron Lasers ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
X Ray Scattering ◽  
X Ray Absorption

Inelastic X-ray scattering techniques enhance chemical speciation by X-ray absorption fine structure (XAFS) spectroscopy and open up application of X-ray free electron lasers to observe chemical transformations.

Kyushu University Beamline, BL06, at SAGA Light Source

2011 ◽  
Vol 1 (SRMS-7) ◽  
Author(s):  
S. Yoshioka ◽  
T. Ishioka ◽  
H. Okabe ◽  
A. Harata ◽  
Y. Sejima ◽  
...  
Keyword(s):  
Light Source ◽  
Focal Point ◽  
Fluorescence Yield ◽  
Photon Flux ◽  
Focal Distance ◽  
Double Crystal ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Ion Chamber ◽  
Double Crystal Monochromator

Kyushu University has installed the hard X-ray beamline, BL06, at bending magnet source of SAGA Light Source in Japan. It is designed for X-ray absorption fine structure (XAFS) spectroscopy and small-angle X-ray scattering (SAXS) experiments. The X-ray energy covered by the beamline ranges from 2.1 to 23 keV using a Si(111) flat double-crystal monochromator. Two bent cylindrical-type focusing mirrors are used, each with a different focal point. They are set in the optics section and can be used independently. One of the mirrors has a focal distance of 6 m, which corresponds to the sample stage for XAFS experiments, while the second mirror focuses at 10 m, corresponding to the detector for the SAXS experiments. The photon flux measured by the ion chamber at mirror focal point is 1010 phs/s. The experimental hutch houses the detection equipment for both XAFS and SAXS. For XAFS studies, a set of ion chambers for transmission mode and a Lytle detector and a Si drift detector for fluorescence yield mode are available. For SAXS studies, the camera pass length can be chosen from 0.5 to 2.5 m with 0.5 m increments in between, and an image plate is operated as signal detector. The beamline will be opened for user operation around summer 2010.

scholarly journals Properties of Impact-Related Pseudotachylite and Associated Shocked Zircon and Monazite in the Upper Levels of a Large Impact Basin: a Case Study From the Vredefort Impact Structure

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1053
Author(s):  
Elizaveta Kovaleva ◽  
Roger Dixon
Keyword(s):  
Impact Crater ◽  
Shock Pressure ◽  
Initial Structure ◽  
Impact Structure ◽  
Near Surface ◽  
X Ray ◽  
Host Rocks ◽  
The Impact

The Vredefort impact structure in South Africa is deeply eroded to its lowermost levels. However, granophyre (impact melt) dykes in such structures preserve clasts of supracrustal rocks, transported down from the uppermost levels of the initial structure. Studying these clasts is the only way to understand the properties of already eroded impactites. One such lithic clast from the Vredefort impact structure contains a thin pseudotachylite vein and is shown to be derived from the near-surface environment of the impact crater. Traditionally, impact pseudotachylites are referred to as in situ melt rocks with the same chemical and isotopic composition as their host rocks. The composition of the sampled pseudotachylite vein is not identical to its host rock, as shown by the micro-X-ray fluorescence (µXRF) and energy-dispersive X-ray (EDX) spectrometry mapping. Mapping shows that the melt transfer and material mixing within pseudotachylites may have commonly occurred at the upper levels of the structure. The vein is spatially related to shocked zircon and monazite crystals in the sample. Granular zircons with small granules are concentrated within and around the vein (not farther than 6–7 mm from the vein). Zircons with planar fractures and shock microtwins occur farther from the vein (6–12 mm). Zircons with microtwins (65°/{112}) are also found inside the vein, and twinned monazite (180°/[101]) is found very close to the vein. These spatial relationships point to elevated shock pressure and shear stress, concentrated along the vein’s plane during impact.

scholarly journals Provenancing variscite beads: Pico Centeno (Encinasola, Spain) outcrop case study

2013 ◽  
Vol 1 (1) ◽  
pp. 17
Author(s):  
Carlos P. Odriozola ◽  
José A. Linares-Catela ◽  
Victor M. Hurtado-Pérez
Keyword(s):  
Trace Elements ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Atomic Ratio ◽  
Mining District ◽  
Copper Age ◽  
X Ray ◽  
Phosphate Species ◽  
Megalithic Tombs

In this study we discuss the exploitation and exchange of variscite at Pico Centeno mining district during the Copper Age. X-ray fluorescence and diffraction (XRF and XRD, respectively) and Fourier transform infrared spectroscopy (FTIR) analyses of the mineral recovered at Pico Centeno mining district provides a baseline mineral signature, which was then compared to other Iberian sources and beads from SW Iberian megalithic tombs. We found that the concentrations of trace elements don not allow establishing provenance of the beads, as traditionally claimed. Instead we found that different proportions of phosphate species, which results in P/Al ratios higher than 1, arose during the genesis of the variscite deposits, modifying the concentrations of PO4 3–, H2PO4– and HPO4 2–. Thus, the P/Al atomic ratio should be an indication of provenance as it is established during mineral genesis.

scholarly journals Poisson vs. Gaussian statistics for sparse X-ray data: Application to the soft X-ray spectrometer

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Shinya Yamada ◽  
Magnus Axelsson ◽  
Yoshitaka Ishisaki ◽  
Saori Konami ◽  
Nozomi Takemura ◽  
...  
Keyword(s):  
Energy Resolution ◽  
Calibration Data ◽  
X Ray ◽  
Poisson Statistics ◽  
Data Application ◽  
Gaussian Statistics ◽  
The Difference ◽  
Counting Statistics ◽  
The Impact ◽  
Proper Consideration

Abstract Reliable results when fitting X-ray data require proper consideration of the statistics involved. We probe the impact of Gaussian versus Poisson statistics at low count levels using both the standard χ2 method and maximum likelihood based on Poisson (C) statistics. The difference is studied and quantified through simulated spectra with known properties. We then test the results through analysis of Mn Kα calibration data taken with the flight spare microcalorimeter for the Hitomi soft X-ray spectrometer. Through comparison with simulations, our results show that the χ2 method tends to give overly optimistic estimates of the detector energy resolution, in particular when there are few counts. Given an energy resolution of ∼5 eV and a line with about 100 photons, the line width becomes ∼10% lower in the χ2 method than in Poisson statistics. This is a consequence of the uncertainties being dominated by counting statistics, and therefore highlights the need to choose the appropriate fit statistic.

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