The University of Missouri gamma-ray scattering facility

doi:10.1016/0029-554X(79)90509-3

Nuclear Instruments and Methods

Volume 166, Issue 1, 1 November 1979, Pages 39-43

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Abstract

The field of gamma-ray scattering is new and only a few of the possible applications of the technique have been pursued. At the University of Missouri Research Reactor (MURR) we are presently completing two instruments to perform studies not previously attempted. The first instrument is a full-circle diffractometer with additional differential ω-motion and linear drive system for the detector which will be used for accurate crystallographic structure measurements at either 0.125 Å (¹⁵³Sm) or 0.03 Å (¹⁹⁸Au). The reduced absorption and extinction at these wavelengths should permit more accurate structure factor determination than has been possible with either X-rays or neutrons. A unique source irradiation system and shield cask have been designed to permit the utilization of relatively large, extremely intense sources. The cask is self-centering at the instrument and has a built in rotation of the source container to maximize the intensity. A large exit aperture is provided in the vertical direction (∼3″) to give extra intensity when tight collimation is not required in that direction.

The second instrument will be using the 103 keV photons from ¹⁵³Sm as a Mössbauer source and will detect inelastically scattered photons with a centrifugally driven absorber. Because of the high specific activities attainable in the flux trap at MURR (∼6000 Ci/g for enriched ¹⁵²Sm) these experiments should be possible where such studies with traditional sources, e.g., ⁵⁷Fe, have not succeeded.

References (5)

J.R. Schneider
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J.R. Schneider
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There are more references available in the full text version of this article.

Cited by (4)

A gamma-ray diffraction instrument for high-intensity Mössbauer sources
1986, Nuclear Inst. and Methods in Physics Research, B
A Mössbauer gamma-ray diffraction instrument has been developed which utilizes high intensity sources produced by neutron irradiation. Most of the early work has used 70 Ci, 5.1 d ¹⁸³Ta sources produced by double neutron capture which yield 12 × 10¹⁰ photons/s for the 46.5 keV Mössbauer transition in ¹⁸³W. A dewar is enclosed in the shielding cask which allows sources to be cooled to 77 K. Samples are located approximately midway between source and detector, which are separated by 155 cm. Collimators in front of the sample and detector commonly limit the beam to 3 mm wide by 25 mm high. A 27% minimum is seen in the velocity spectrum for the 46.5 keV photons scattered from the 200 Bragg reflection in LiF taken in transmission. Enriched, room temperature absorbers mounted on a rotor can be Doppler-shifted up to 17 meV. Q-space resolution of 0.01 Å⁻¹ is significantly better than that reported by other groups using Mössbauer scattering. When a microfoil internal conversion electron (MICE) detector is used, the instrument has the potential for directly measuring the energy transferred by the inelastically scattered photons, especially for low energy excitations in solids which require high energy resolution.
Gamma-ray crystallography and related techniques
1982, Nuclear Instruments and Methods
Use of gamma-ray diffraction has now been successfully demonstrated for accurate extinction-free structure factor measurements, but no complete crystallographic studies have been performed using gamma-ray techniques. Recently, we have taken data using 0.12 Å gamma-rays (¹⁵³Sm) on Mg₂SiO₄ and BeO which demonstrate for the first time the ability to perform “normal” crystallographic studies with gamma-rays. To make this technique accessible to a more general community we have designed a new instrument using 0.2 Å gamma radiation (¹⁶⁹Yb) and a special detector which could be set up in any X-ray laboratory. We have also demonstrated the feasibility of powder diffraction studies with gamma-rays which hold significant advantages over X-ray techniques and could also be set up in an X-ray laboratory. A gamma-ray Compton scattering spectrometer using 320 keV radiation (⁵¹Cr) is being designed and will be used to determine momentum density distributions. Finally, a quasi-elastic scattering instrument using an intense (1000 Ci) Mossbauer source and a conversion electron detector is partially completed and should open some new areas of research when operational.
Electron density in sodium fluoride by -ray diffractometry
1982, Physical Review B
Crystal perfection of HgI<inf>2</inf> studied by neutron and gamma-ray diffraction
1981, Journal of Applied Physics

^☆: Work supported by the National Science Foundation.

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The University of Missouri gamma-ray scattering facility☆

Abstract

J. Appl. Cryst.

J. Appl. Cryst.