The Neutron Powder Diffractometer is a versatile instrument, able to examine a variety of materials. With low angular coverage and a clean background, HB-2A is particularly well-suited to studying new, complex, magnetically ordered systems. The use and development of extreme sample environments of temperature, magnetic field, and pressure allows the necessary wide area of phase space to be accessed to investigate novel phenomena in new materials.
The HB-2A Neutron Powder Diffractometer is a workhorse instrument used to conduct crystal and magnetic structural studies of powdered and ceramic samples as a function of intensive conditions (such as temperature, pressure, and magnetic field). Powder diffraction data collected on this instrument are ideally suited for the Rietveld method. A full range of ancillary sample environments can be used, including cryofurnaces (4–800 K), furnaces (up to 1800 K), cryostats (up to 0.03 K), and cryomagnets (up to 8 T).
The Neutron Powder Diffractometer has a Debye-Scherrer geometry. The detector bank has 44 3He tubes with 12' Soller collimators. A germanium wafer-stack monochromator is vertically focusing and provides one of three principal wavelengths depending on which reflection is in the diffracting condition: (113) 2.41 Å, (115) 1.54 Å, or (117) 1.12 Å. The take-off angle from the monochromator is fixed at 90°, and the minimum peak full width at half maximum (FWHM) is 0.2°. There are two choices of premonochromator collimation (α1 = 12' or open) and three choices of pre-sample collimation (α2 = 16', 21', or 31') that allow the operation of the instrument in high-resolution or high-intensity modes.
Technologically important and scientifically driven materials amenable to study by neutron powder diffraction include (but are not limited to) superconductors, multiferroics, catalysts, ionic conductors, alloys, intermetallic compounds, ceramics, cements, colossal magnetoresistance perovskites, magnets, minerals, waste forms, hydrogen storage materials, thermoelectrics, zeolites, and pharmaceuticals. In addition to traditional crystal structural refinements, studies of phase transitions, thermal expansion, quantitative analysis, residual stress, and ab initio structure solution can be undertaken from the powder data.
|Monochromator:||Vertically focusing Germanium|
|Monochromator angle:||2Θm = 90°|
|Wavelengths:||λ=1.54 Å(115), 2.41 Å(113), 1.12 Å(117)|
|Scattering angles:||0° < 2Θ < 155°|
|Sample angle:||0° < ω < 360°|
|Collimations (FWHM):||Premonochromator (α1): 12′ or open (60′ effective)|
Monochromator - Sample (α2): 16′, 21′, or 31′
Sample - Detector (α3): 12′
|Detector Bank:||44 3He detectors|
|Beam Size:||25 × 25 mm2 at sample position|
|Resolution:||2 × 10-3 Δd/d|