Capabilities of the WAND Instrument

The HFIR HB-2C Wide Angle Neutron Diffractometer (WAND) is a dual purpose instrument that can be used as a fast coarse-resolution powder diffractometer or as a single crystal diffractometer to explore broad regions of reciprocal space. This instrument is most beneficial to the condensed matter, materials science, as well as the planetary sciences communities. Due to its versatility and easy access this instrument can be used for parametric studies using a variety of ancillary sample environments to provide a complete control of thermodynamic variables such as temperature, magnetic field, and pressure. Most of the recent demand for this instrument has been focused in studies of unconventional superconductors, low-dimensional magnets, multiferroics and geophysics.

Additional information of recent experiments carried out at WAND are listed on the instrument's Publications page. 

Powder diffraction
Medium resolution powder diffraction in the Q range 0.2 to 8.2 Å-1. The left picture shows the silicon standard powder pattern for calibration. On the right side a user experiment (Daniel Haynes, Mark Smith, Devendra Pakhare, National Energy Laboratory) investigated the in-situ calcination process I a La-Ni-Zr compound. WAND can take data without detector movement which allows measurements while ramping for instance temperature.

 

 

Single crystal diffraction – superstructures
WAND can be used to map the reciprocal space for a defined orientation. In this example the HHL reciprocal plane of Pr2NiO4+δ shows that the excess oxygen forms a well-defined superstructure which produces weak additional reflections (24s/sample angle, 180° rotation 0.2° step, m~1g).

 

 

Single crystal diffraction – diffuse scattering
Reciprocal mapping gives the possibility to investigate short-range correlations for example the reciprocal map of the HK0 plane of Ho2PdSi3. The map is the difference plot 10 K - 50 K which leaves only the strong diffuse critical magnetic scattering around the crystallographic Bragg peak positions (TN = 7K). (20s/sample angle, 180° rotation 0.1° step, m=2.9g). 

 

 

 

Single crystal diffraction – small samples
The low background on WAND enables also the study of small single crystals. In this example (m = 3.6 mg) we found the magnetic Bragg peaks on the {100} positions. (60s/sample angle, 180° rotation 0.2° step)

 

 

 

High Pressure Neutron Diffraction
We try to widen the availability of high pressure cells on WAND. Here, we followed the magnetic structure in the multiferroic CuCrO2 using a Ni-Cr-Al pressure cell (photo on the right side). The magnetic Bragg peaks at low pressure are close to (1/3 1/3 L) for integer values of L (left side of the plot). At 2 GPa the peak position remains on (1/3 1/3 L), but L has now non-integer value and the reflections broaden considerably along the L direction (right side of the plot).