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Instrumental resolution as a function of scattering angle and wavelength as exemplified for the POWGEN instrument

Journal Article · · Journal of Applied Crystallography (Online)
 [1];  [2];  [3];  [4];  [2]
  1. RWTH Aachen Univ. (Germany); DOE/OSTI
  2. RWTH Aachen Univ. (Germany)
  3. European Spallation Source (ESS), Lund (Sweden); Juelich Centre for Neutron Science (JCNS) and Peter Grünberg Institute (PGI), Forschungszentrum Juelich GmbH (Germany)
  4. RWTH Aachen Univ. (Germany); Independent University of Moscow (Russian Federation)
+ Show Author Affiliations
The method of angular- and wavelength-dispersive (e.g. two-dimensional) Rietveld refinement is a new and emerging tool for the analysis of neutron diffraction data measured at time-of-flight instruments with large area detectors. Following the approach for one-dimensional refinements (using either scattering angle or time of flight), the first step at each beam time cycle is the calibration of the instrument including the determination of instrumental contributions to the peak shape variation to be expected for diffraction patterns measured by the users. The aim of this work is to provide the users with calibration files and – for the later Rietveld refinement of the measured data – with an instrumental resolution file (IRF). This article will elaborate on the necessary steps to generate such an IRF for the angular- and wavelength-dispersive case, exemplified for the POWGEN instrument. A dataset measured on a standard diamond sample is used to extract the profile function in the two-dimensional case. It is found that the variation of reflection width with 2θ and λ can be expressed by the standard equation used for evaluating the instrumental resolution, which yields a substantially more fundamental approach to the parameterization of the instrumental contribution to the peak shape. Geometrical considerations of the POWGEN instrument and sample effects lead to values for Δθ, Δt and ΔL that yield a very good match to the extracted FWHM values. In a final step the refinement results are compared with the one-dimensional, i.e. diffraction-focused, case.
Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1625772
Journal Information:
Journal of Applied Crystallography (Online), Journal Name: Journal of Applied Crystallography (Online) Journal Issue: 3 Vol. 50; ISSN 1600-5767
Publisher:
International Union of CrystallographyCopyright Statement
Country of Publication:
United States
Language:
English

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Figures / Tables (13)

Table 1(p. 2)table Table 1
Figure 1(p. 3)figure Figure 1
Figure 2(p. 3)figure Figure 2
Figure 3(p. 4)figure Figure 3
Table 2(p. 4)table Table 2
Figure 4(p. 5)figure Figure 4
Table 3(p. 6)table Table 3
Table 4(p. 6)table Table 4
Figure 5(p. 7)figure Figure 5
Table 5(p. 7)table Table 5
Figure 6(p. 8)figure Figure 6
Figure 7(p. 8)figure Figure 7
Table 6(p. 8)table Table 6

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Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
Chemistry
Crystallography
POWGEN
angular- and wavelength-dispersive Rietveld refinement
instrumental resolution
neutron diffraction
powder methods
time of flight