Path length dependent neutron diffraction peak shifts observed during residual strain measurements in U–8 wt% Mo castings

Journal Article · 16 May 2017 · Journal of Applied Crystallography (Online)

DOI: https://doi.org/10.1107/S1600576717005295 · OSTI ID:1356243

Steiner, M. A. ^[1]; Bunn, J. R.  ^[2]; Einhorn, J. R.  ^[1]; Garlea, E. ^[3]; Payzant, E. A.  ^[2]; Agnew, S. R. ^[1]

---

1. Univ. of Virginia, Charlottesville, VA (United States). Dept. of Material Science and Engineering
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
3. Y-12 National Security Complex, Oak Ridge, TN (United States)

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.

• Research Organization: Oak Ridge Y-12 Plant (Y-12), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: NA0001942
• OSTI ID: 1356243
• Report Number(s): MS/GAR--170320
• Journal Information: Journal of Applied Crystallography (Online), Journal Name: Journal of Applied Crystallography (Online) Journal Issue: 3 Vol. 50; ISSN JACGAR; ISSN 1600-5767
• Publisher: International Union of CrystallographyCopyright Statement
• Country of Publication: United States
• Language: English