Path length dependent neutron diffraction peak shifts observed during residual strain measurements in U–8 wt% Mo castings. Issue 3 (16th May 2017)

• Record Type: Journal Article
• Authors: Steiner, M. A.; Bunn, J. R.; Einhorn, J. R.; Garlea, E.; Payzant, E. A.; Agnew, S. R.
• Is Part Of: Journal of applied crystallography. Volume 50:Issue 3(2017)
• Page Start: 851
• Page End: 858
• Publication Date: 2017-05-16
• Subjects: neutron diffraction -- residual stress mapping -- strain measurement -- U–Mo -- focusing monochromators -- attenuation; Crystallography -- Periodicals; 548.05
• DOI: 10.1107/S1600576717005295
• Languages: English
• ISSNs: 0021-8898

Abstract

Abstract : This study reports an angular diffraction peak shift that scales linearly with the neutron beam path length traveled through a diffracting sample. A hypothesis for the origin of this shift is presented, based upon non‐ideal focusing of the neutron monochromator in combination with changes to the wavelength distribution reaching the detector due to factors such as attenuation. Abstract : This study reports an angular diffraction peak shift that scales linearly with the neutron beam path length traveled through a diffracting sample. This shift was observed in the context of mapping the residual stress state of a large U–8 wt% Mo casting, as well as during complementary measurements on a smaller casting of the same material. If uncorrected, this peak shift implies a non‐physical level of residual stress. A hypothesis for the origin of this shift is presented, based upon non‐ideal focusing of the neutron monochromator in combination with changes to the wavelength distribution reaching the detector due to factors such as attenuation. The magnitude of the shift is observed to vary linearly with the width of the diffraction peak reaching the detector. Consideration of this shift will be important for strain measurements requiring long path lengths through samples with significant attenuation. This effect can probably be reduced by selecting smaller voxel slit widths.