Powder diffraction in Australia

Abstract

The high-resolution powder diffractometer (HRPD) at the HIFAR reactor has been a reliable research tool for over twenty years in a number of configurations [1]. The diffractometer shares beamline 4H1 with the higher intensity, medium-resolution powder diffractometer. The design of the HRPD is based on that of DIA at the Institut Laue Langevin. It uses a simple Ge single crystal monochromator with a fixed take-off angle of 120°. The monochromator provides monochromatic beams of neutrons at a number of wavelengths by rotation around [1 −1 0], the most commonly requested being λ = 1.32, 1.49, and 1.88Å. This monochromator will shortly be replaced with a focusing monochromator at the same take-off angle. The detector system consists of 24 3He detectors that can cover the angular range 5 < 2θ < 155° at step intervals of 0.05°. The best resolution of the diffractometer is Δd/d = 2 × 10−3. Typically it takes approximately twenty-four hours to collect a pattern, and a representative pattern is shown in Figure 1.