Single Crystal Diffractometer (TOPAZ)

Instrument overview: Cutout of instrument enclosure with the interchangeable optics upstream of the detector arrangement surrounding the sample position and environment. Downstream are get lost tube and beam stop. Electronics and support equipment is along the back wall of the enclosure. Behind the enclosure are computer and data analysis room (top level) and sample preparation facilities (bottom level). Click image for a larger view.

The TOPAZ Single Crystal Diffractometer (SCD) is part of the SNS Instruments Next Generation Project (SING) and is scheduled for commissioning early in FY2009. TOPAZ will address problems and greatly expand the range of materials explored in chemistry, earth sciences, materials science and engineering, solid-state physics, and biology.

TOPAZ SCD is designed to perform elastic scattering experiments under controlled environmental conditions to probe material structures and responses. Enabling to measure the same single crystal sample with neutron as with X-ray diffraction was the guiding design principle of TOPAZ.

Data will be collected on samples of (0.1 mm)3 or less. Resolution is such that an average unit cell size of [50 x 50 x 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 to biology and medical applications.

Materials to be investigated using TOPAZ include functional materials of the high Tc superconductor perovskite structure family, magnetic superstructures in perovskites and spinels. Potential future high-density, three dimensional storage materials on molecular basis, known as single molecule magnets [SMMs] have raised much interest but could mostly only be studied in polycrystalline samples with neutron diffraction. Also of importance are catalytic precursors, metalhydride materials for potential hydrogen storage applications, and organometallics.

View inside the sample enclosure: in front are the interchangeable focusing optics within 2 m upstream of the sample. This allows focusing between an area of 0.1 mm x 0.1 mm and 3 mm x 3 mm. The fully populated detector array with sample loading from the top encloses the sample position spherically.

Neutron single crystal diffraction is uniquely positioned to decipher the pathways and bonding of hydrogen in 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 to investigate magnetic and spin density studies in magnetically interesting materials.

TOPAZ/MaNDi IDT Meeting Report (PDF) - May 30, 2008