Instrument Description

TOPAZ is an elastic scattering instrument that allows for probing of material structures and responses under controlled environmental conditions. It enables neutron measurement of the same single-crystal samples that is possible with x-ray diffraction.

Data are collected on samples of 0.1 mm3 or less. Resolution is such that an average unit cell size of [50 × 50 × 50] Å3 for compounds of moderate complexity can be easily accommodated. This includes inorganic large and porous framework and guest-host materials, metal (in-)organic cluster and molecular compounds, and organic arrangements of interest for biology and medical applications.

Applications

Materials investigated with TOPAZ include functional materials of the high Tc superconductor perovskite structure family, magnetic superstructures in perovskites, and spinels. Also of importance are catalytic precursors, metalhydride materials for potential hydrogen storage applications, and organometallics. Potential future studies include high-density, three-dimensional storage materials, known as single molecule magnets. These materials have raised much interest but in the past could mostly be studied only in polycrystalline samples using neutron diffraction.
Neutron single-crystal diffraction is uniquely positioned to decipher the pathways and bonding of hydrogen in the presence of heavy metal ions as it is sensitive to both classes of elements in comparable quantity. Simultaneously, the magnetic ordering and structure can be investigated exploring the fact the neutrons carry a magnetic moment. This allows for investigation of magnetic and spin density studies in magnetically interesting materials.

Specifications

ModeratorDecoupled poisoned hydrogen
Source to sample distance18 m
Sample to detector distance, evacuated39 – 45 cm
Initial angular detector coverage1.7 sr, 14 detectors
Optional angular detector coverage> 2.9 sr
Detector pixel size~1.0 mm
Detector angles20–160º 2θ; +/- 32° out-of-plane
Wavelength bandwidth3.0 Å
Frame 10.5 – 3.5 Å
Frame 24.0–7.0 Å
Resolution0.4%
Sample size1–10 mm3 (<3 mm on a side)
d spacing range0.25 < 12.5 < 25.0 Å (Fame 1, 2)
Neutron beam divergence on sample15 mrad < d < 25 mrad
Sample EnvironmentAmbient 2-circle goniometer:
χ = 135°, ω: 0° – 360°, Φ: 0° – 360°
Nitrogen cold flow 100–400 K

Frequently Asked Questions

Q. What types of crystals are suitable for TOPAZ?
A. TOPAZ is designed for sample sizes comparable to those used with x-ray diffraction. Samples with unit cells as high as 50 Å can be accommodated.
Q. How long does it take to gather data?
A. This depends on the complexity of the sample structure and unit cell size. However, for a moderately sized unit cell (~30 Å), times are on the order of minutes, rather than hours.
Q. What sample environment conditions are available?
A. Various crystal sample envirments are available, specifically cryogenic cooling, magnetic fields, and heating. In addition, TOPAZ can accomodate scattering with polarized neutrons.