Neutron Powder Diffractometer

POWDER |  HB-2A | HFIR

Neutron Powder Diffractometer

Mission Statement

The Neutron Powder Diffractometer (HB-2A) 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.

Instrument Description

HB-2A conducts magnetic and crystal structural studies of powdered and ceramic samples as a function of intensive conditions from 0.03 - 1800 K, up to 8 T, and up to 2 GPa.

HB-2A has a Debye-Scherrer geometry. The moveable detector bank has 44 3He tubes with 12' Soller collimators, spaced by ~2.5° in 2Θ. A germanium wafer-stack monochromator is vertically focusing and provides one of three principal wavelengths, depending on which reflection is in the diffracting condition: Ge(113) 2.41 Å, Ge(115) 1.54 Å, or Ge(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), which is open, 60; effective, and via three choices of presample collimation (α2 = 16', 21', or 31'). The instrument can operate in polarized mode with the use of a polarizing supermirror V-cavity optimized for the 2.41 Å wavelength.

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.

Applications

Scientifically important and technologically applicable materials amenable to study by neutron powder diffraction include (but are not limited to):

  • Quantum magnets
  • Superconductors
  • Multiferroics
  • Catalysts
  • Intermetallic compounds
  • Ionic conductors
  • Alloys
  • Colossal magnetoresistance perovskites
  • Minerals
  • Hydrogen storage materials
  • Thermoelectrics

Specifications

Beam Spectrum Thermal
Monochromator Vertically focusing Germanium
Monochromator angle 2Θm = 90°
Wavelengths λ=1.54 Å, 2.41 Å, 1.12 Å
Scattering angles 2° < 2Θ < 155°
Sample angle 0° < ω < 360°
Collimations (FWHM) Premonochromator (α1): open (60′ effective)
Monochromator - Sample (α2): 16′, 21′, or 31′
Sample - Detector (α3): 12′
Detector Bank 44 3He detectors
Beam Size 50 × 25 mm2 at sample position
Resolution 2 × 10-3 Δd/d