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Title: Rotation of X-ray polarization in the glitches of a silicon crystal monochromator

Abstract

EXAFS studies on dilute samples are usually carried out by collecting the fluorescence yield using a large-area multi-element detector. This method is susceptible to the `glitches' produced by all single-crystal monochromators. Glitches are sharp dips or spikes in the diffracted intensity at specific crystal orientations. If incorrectly compensated, they degrade the spectroscopic data. Normalization of the fluorescence signal by the incident flux alone is sometimes insufficient to compensate for the glitches. Measurements performed at the state-of-the-art wiggler beamline I20-scanning at Diamond Light Source have shown that the glitches alter the spatial distribution of the sample's quasi-elastic X-ray scattering. Because glitches result from additional Bragg reflections, multiple-beam dynamical diffraction theory is necessary to understand their effects. Here, the glitches of the Si(111) four-bounce monochromator of I20-scanning just above the Ni Kedge are associated with their Bragg reflections. A fitting procedure that treats coherent and Compton scattering is developed and applied to a sample of an extremely dilute (100 micromolal) aqueous solution of Ni(NO 3) 2. The depolarization of the wiggler X-ray beam out of the electron orbit is modeled. The fits achieve good agreement with the sample's quasi-elastic scattering with just a few parameters. The X-ray polarization is rotated up tomore » ±4.3° within the glitches, as predicted by dynamical diffraction. These results will help users normalize EXAFS data at glitches.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
Diamond Light Source, UK
OSTI Identifier:
1376895
DOE Contract Number:
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Crystallography (Online); Journal Volume: 49; Journal Issue: 4
Country of Publication:
United States
Language:
English

Citation Formats

Sutter, John P., Boada, Roberto, Bowron, Daniel T., Stepanov, Sergey A., and Díaz-Moreno, Sofía. Rotation of X-ray polarization in the glitches of a silicon crystal monochromator. United States: N. p., 2016. Web. doi:10.1107/S1600576716009183.
Sutter, John P., Boada, Roberto, Bowron, Daniel T., Stepanov, Sergey A., & Díaz-Moreno, Sofía. Rotation of X-ray polarization in the glitches of a silicon crystal monochromator. United States. doi:10.1107/S1600576716009183.
Sutter, John P., Boada, Roberto, Bowron, Daniel T., Stepanov, Sergey A., and Díaz-Moreno, Sofía. 2016. "Rotation of X-ray polarization in the glitches of a silicon crystal monochromator". United States. doi:10.1107/S1600576716009183.
@article{osti_1376895,
title = {Rotation of X-ray polarization in the glitches of a silicon crystal monochromator},
author = {Sutter, John P. and Boada, Roberto and Bowron, Daniel T. and Stepanov, Sergey A. and Díaz-Moreno, Sofía},
abstractNote = {EXAFS studies on dilute samples are usually carried out by collecting the fluorescence yield using a large-area multi-element detector. This method is susceptible to the `glitches' produced by all single-crystal monochromators. Glitches are sharp dips or spikes in the diffracted intensity at specific crystal orientations. If incorrectly compensated, they degrade the spectroscopic data. Normalization of the fluorescence signal by the incident flux alone is sometimes insufficient to compensate for the glitches. Measurements performed at the state-of-the-art wiggler beamline I20-scanning at Diamond Light Source have shown that the glitches alter the spatial distribution of the sample's quasi-elastic X-ray scattering. Because glitches result from additional Bragg reflections, multiple-beam dynamical diffraction theory is necessary to understand their effects. Here, the glitches of the Si(111) four-bounce monochromator of I20-scanning just above the Ni Kedge are associated with their Bragg reflections. A fitting procedure that treats coherent and Compton scattering is developed and applied to a sample of an extremely dilute (100 micromolal) aqueous solution of Ni(NO3)2. The depolarization of the wiggler X-ray beam out of the electron orbit is modeled. The fits achieve good agreement with the sample's quasi-elastic scattering with just a few parameters. The X-ray polarization is rotated up to ±4.3° within the glitches, as predicted by dynamical diffraction. These results will help users normalize EXAFS data at glitches.},
doi = {10.1107/S1600576716009183},
journal = {Journal of Applied Crystallography (Online)},
number = 4,
volume = 49,
place = {United States},
year = 2016,
month = 7
}
  • An experiment was performed on beamline BL 3 at the European Synchrotron Radiation Facility to test the diffraction performance of a novel internally liquid-nitrogen-cooled, thin silicon crystal monochromator exposed to high heat loads. The beam parameters were chosen to closely match the conditions expected, in terms of absorbed power and beam profile, at the Advanced Photon Source (APS) for the closed gap undulator at 7 GeV and 100 mA. The cooled crystal was oriented at 11.4{degree} in the symmetric Bragg geometry to diffract 30 keV x-rays from the Si(333) planes. The source was a 44-pole wiggler with the insertion devicemore » gap set at 25.0 mm corresponding to a deflection parameter, {ital K}, of 4.2. A tunable toroidal mirror was used to focus the wiggler beam onto the crystal. Double-crystal rocking curves were measured at several power values using different attenuators. The maximum total power absorbed by the 0.6-mm-thick crystal was 154 W at a storage ring current of 136 mA. The peak power density at normal incidence was about 420 W/mm{sup 2} corresponding to an absorbed peak power density on the crystal face of 83 W/mm{sup 2}. No thermal-induced broadening of the rocking curve was observed above the average measured mounting/fabrication strain of 2 arcsec. Rocking curves were also measured as a function of coolant flow rate and pressure. No systematic broadening occurred due to flow-induced vibrations up to 6 l/min. It has been demonstrated that thin silicon crystals directly cooled with liquid nitrogen can handle high power density synchrotron beams comparable to what is expected for the APS undulators with no appreciable thermal deformation.« less
  • To predict the performance of the cryogenically cooled silicon crystal, intensive studies have been carried out to sort out the influences of various parameters, such as heat load power and power distribution, cooling coefficient, and beam size. The thermal slope error of the crystal is calculated by finite element modeling. Quadratic law was applied to calculate the rocking-curve width. Heat load tests were also performed with a channel-cut silicon monochromator on beamline ID09 at the European Synchrotron Radiation Facility (ESRF). The silicon crystal is indirectly cooled from the sides by liquid nitrogen. Measured rocking-curve widths are compared with those calculatedmore » by finite element modeling. When we include the broadening from the intrinsic rocking-curve width and mounting strain, the calculated rocking-curve width versus heat load is in excellent agreement with experiment.« less
  • Liquid-N2-cooled Si crystals replaced water-cooled diamond crystals for the double-crystal monochromator on the JAERI beamline, BL11XU, at SPring-8. To use the whole energy from 6 to 70 keV, we adopted the system of dual symmetric Si geometry, Si(111)/Si(311), which can be switched by a horizontal translation (x) stage perpendicular to the beam axis. The characterization of the crystals was performed by the use of both the x-ray generator and the synchrotron radiation from the undulator. The observed intensities and rocking curves resulted in that each crystal was good for BL11XU and that the performance of x-ray reflection was highly improved.
  • Here, a mathematical technique has now been developed that reveals the underlying dynamics of time-dependent data collected with extreme temporal uncertainty, without using additional, costly instrumentation.