The small-angle neutron scattering spectrometer at the University of Missouri research reactor

Abstract

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/~ with a wavelength spread of approximately 4.1~o. 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 3He detectors as an economic alternative to a crossed-wire twodimensional multi-detector. An array of 43 positionsensitive 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 areaaveraged detector efficiency is about 84~o at a wavelength of 4.75 A. The range of scattering vectors that can be measured is 0.005<Q<0.15 A-1. The instrument is well suited to a wide variety of experiments on specimens having characteristic dimensions between 30 and 500 A. 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.

Forward scattering of 4·75 }5 neutrons in hydrogenous liquids

“…Most measurements were made on the MURR facility (Mildner, Berliner, Pringle & King, 1981) with a source iris of 2"0 cm diameter, a sample iris of 1.0 cm diameter and matched flight paths of 4.59 m. A special sample holder was used such that the sample could be 0021-8898/88/060818-05503.00 © 1988 International Union of Crystallography backed by a second cadmium iris of 1.05 cm diameter, thus creating a cadmium-sample-cadmium sandwich. Pairwise measurements were made with and without the back iris to determine the contribution to intensity from multiple scattering in sample space hidden behind the standard sample iris.…”

Adapting a triple-axis spectrometer for small angle neutron scattering measurements

“…Although there are ways to increase ⌬ / , they usually involve a cost prohibitive redesign of the instrument. [4][5][6][7][8] Another method of increasing incident neutron flux, while not increasing the beam size, is to employ multiple incident beams which converge at a single spot on the detector. This concept of one-dimensional confocal beams was first proposed and tested by Nunes 9 and was further developed into two-dimensional ͑2D͒ confocal beams by Glinka, et al 10 At CNBC we have designed and implemented a confocal Soller collimator ͑CSC͒ for use at the N5 triple-axis spectrometer, making it suitable for SANS measurements.…”

An X-ray microdiffractometer for the analysis of small specimens, and its use in a forensic science laboratory

“…For the reactor instrument at M URR, the resolution has been worked out in detail and has been verified experimentally (Mildner, et al, 1981). For the measurement of Borso et al (1982), AQ is 0.0035 ,~,-1.…”