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The small‐angle neutron scattering spectrometer at the University of Missouri research reactor
Author(s) -
Mildner D. F. R.,
Berliner R.,
Pringle O. A.,
King J. S.
Publication year - 1981
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889881009631
Subject(s) - spectrometer , optics , neutron , detector , scattering , research reactor , beam (structure) , neutron radiation , small angle scattering , neutron scattering , physics , path length , small angle neutron scattering , time of flight , neutron detection , bragg's law , materials science , nuclear physics , diffraction
A small‐angle neutron scattering (SANS) spectrometer has been constructed at the University of Missouri Research Reactor Facility (MURR). The design of the MURR–SANS is unusual in that the size of the reactor containment building constrains the flight path to be vertical. This is achieved by Bragg scattering upward through 90° from a set of slightly misaligned pyrolytic graphite crystals to provide a neutron beam at 4.75 Å with a wavelength spread of approximately 4.1%. The beam incident on the sample is defined by two matched variable apertures located either 3.0 or 4.5 m apart. The evacuated scattered flight path is designed with removable extensions to match the primary flight path in length. The instrument has an automatic sample handling capability provided by its own dedicated PDP 11/03 computer. The detector is a large assembly of commercially available linear 3 He detectors as an economic alternative to a crossed‐wire two‐dimensional multi‐detector. An array of 43 position‐sensitive proportional counters, 24 in (609.6 mm) long and 0.5 in (12.7 mm) in diameter, using charge division gives a spatial resolution of 5 x 12.7 mm. The area‐averaged detector efficiency is about 84% at a wavelength of 4.75 Å. The range of scattering vectors that can be measured is 0.005 < Q < 0.15 Å −1 . The instrument is well suited to a wide variety of experiments on specimens having characteristic dimensions between 20 and 500 Å. MURR–SANS is designed as a user‐oriented facility which provides both reasonable resolution and intensity on sample at a modest cost, and forms part of a neutron scattering center.