The Performance of the Australian Powder Diffractometer at the Photon Factory, Japan

Australian scientists have built and installed an X-ray powder diffractometer of an unusual design on the Australian beamline at the Photon Factory synchrotron-radiation facility within the National Laboratory for High Energy Physics (KEK), Tsukuba, Japan. The diffractometer is a Debye–Scherrer camera of 0.573 m radius. The place of the cylindrical film in a conventional camera of this type is taken by image plates. To minimize scattering and absorption by air, the instrument can be evacuated. The instrument is now in operation and has been tested with a specimen of the rutile phase of TiO₂. This material has been thoroughly studied previously and it has been demonstrated that time-of-flight neutron powder diffraction, conventional neutron powder diffraction, single-crystal neutron diffraction and single-crystal X-ray diffraction lead to a consistent set of values for the anisotropic thermal parameters and the one positional parameter. The powder specimen of rutile for use at KEK was diluted with gum tragacanth and inserted into a glass capillary of 0.5 mm diameter. The beam from the synchrotron is incident on a silicon (111) channel-cut monochromator. Data were collected to ±165°2θ at wavelengths of 0.62, 1.10, 1.54 and 1.90 Å. The exposure time for each data set was 10 min. The resolution of the instrument agrees with theoretical prediction and is such that the full width at half-maximum of a reflection varies from 0.04° at 20°2θ to 0.2° at 160°2θ for a wavelength of 1.54 Å. The intensity from a 10 min exposure is more than sufficient for Rietveld refinement (R_exp < 1%).