Studying the structure of materials under extreme environments.
One of the challenges of modern technology is to understand how extreme environments interact with materials at the microscopic level and how these interactions can be controlled to develop new materials. The Wide-Angle Neutron Diffractometer (WAND) provides the ability to perform structural studies of materials under a variety of extreme environments like high magnetic fields, high and low temperatures, and high pressures. One of the breakthroughs made possible by this instrument was the study of the effect of high magnetic fields in steels at high temperatures, which allowed a better understanding of the microstructures in these materials. WAND is operated in collaboration with the Japan Atomic Energy Research Institute under the US/Japan Cooperative Program on Neutron Scattering Research.
The HFIR HB-2C WAND instrument was designed to provide two specialized data-collection capabilities: (1) fast measurements of medium-resolution powder-diffraction patterns and (2) measurements of diffuse scattering in single crystals. For these purposes, this instrument is equipped with a curved, one-dimensional 3He position-sensitive detector covering 125º of the scattering angle with the focal distance of 71 cm. This enables measurements of single-crystal diffraction patterns in a short time over a wide range of the reciprocal space, as well as performance of time-resolved experiments for structural transformations having short time constants. The WAND detector (ORDELA 1410N) is a multianode type (624 anodes and a 0.2° pitch) 3He gas counter specially designed for this instrument. This detector has an intrinsic angular resolution of 0.25° and a maximum counting rate per anode of 105 counts/s. The vertical focussing Ge monochromator provides high flux at the sample position which allows fast parametric measurements. The full range of HFIR’s sample environment can be used, including cryofurnaces (4–800 K), furnaces (to 1800 K), cryostats (to 0.06 K), and cryomagnets (to 7 T). The high flux at the sample position also allows high pressure experiments with clamp cells up to 6 GPa.
WAND is ideal for the studies of time-resolved phenomena and diffuse scattering in single crystals. Research performed at WAND includes studies of the growth of ferroelectric ice-XI, hole and charge ordering in colossal magnetoresistance materials, and magnetic structures and correlations in low-dimensional magnetic systems and other magnetic materials.
|Monochromator:||Vertically focused hot pressed Ge|
|Monochromator angle:||2ΘM = 51.5°|
λ = 1.5 Å (Ge 113)
0.95 Å (Ge 115)
|Scattering angles:||0° < 2Θ < 156°|
|Collimations||Oscillating collimator radial before the detector|
|Detector:||Multiwire (624 anodes, 0.2° pitch) 3He curved PSD|
|Resolution||2 mm spatial resolution|