R. F. Garrett

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 A. 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 A. The intensity from a 10 min exposure is more than sufficient for Rietveld refinement (Rexp < 1%).

Powder diffraction using imaging plates at the Australian National Beamline Facility at the Photon Factory

A novel x‐ray diffractometer was installed at the Australian National Beamline Facility at the Photon Factory, Japan, in October 1993. One of the major capabilities of the instrument is high speed high resolution powder diffraction using imaging plate detectors. The diffractometer combines a two circle goniometer and a large cassette in which imaging plates can be loaded covering 320° of 2θ. The diffractometer is enclosed in a large vacuum chamber and can be operated in air, vacuum, or helium. Recently, powder data has been obtained from rutile (TiO2) and NBS Si 640b at wavelengths from 0.62 to 1.9 A using imaging plates, and has been used to characterize the performance of the instrument. The data has been refined using the Rietveld method and R values of under 2% obtained. The resolution of the system varies from a minimum of about 0.04° to around 0.25° at 2θ angles around 160°, which is the equal of most synchrotron based powder diffractometers, and only slightly worse than that obtained using an analy...

Focusing of X-rays by Total External Reflection from a Paraboloidally Tapered Glass Capillary

The first observation of a true geometrical focus of X-rays well beyond the exit of a paraboloidally tapered glass monocapillary is reported. An intensity gain of 250 +/- 20 into a 6 x 9 mum pinhole for 8 keV X-rays and transmission efficiencies of more than 90% below 20 keV were observed.

The Australian diffractometer at the Photon Factory

Outlined are design features of a versatile high‐resolution two‐axis diffractometer that is being constructed for operation at the Photon Factory as an Australian national facility. The instrument features optional use of multiple‐imaging plates on a translating cassette to allow rapid recording of an almost complete range of data covering both the high‐angle and small‐angle scattering regime or alternatively the use of electronic detectors. The instrument will be capable of operation in various modes including the following: (i) high‐resolution powder diffraction with single‐channel counter and crystal analyzer, (ii) high‐resolution, high‐speed powder diffraction in the Debye–Scherrer mode with imaging plates as recording medium, either stationary or translating (for time‐dependent studies), (iii) small‐angle x‐ray scattering with imaging plates as recording medium, (iv) protein crystallography in screenless Weissenberg mode, and (v) two‐ or three‐axis single‐crystal diffractometry. The salient features ...

Protein Crystal Diffraction Patterns Using a Capillary-Focused Synchrotron X-ray Beam

A paraboloidally tapered glass monocapillary was used to focus an 8 keV monochromated synchrotron bending-magnet X-ray beam into a 40 (+/-5) mum focal spot located 45 (+/-5) mm from the exit of the capillary. This focal spot had a measured intensity gain of 120 (+/-10) times the intensity present in an equivalent cross section of the unfocused beam from the monochromator. This focused beam was used to obtain oscillation diffraction patterns on image plates from a hen egg-white lysozyme protein crystal in two distinct geometries: one with the specimen crystal at the capillary exit and the other with the crystal at the beam focus. In the first geometry, focused Bragg reflections were observed at the focal plane. In the second geometry, diverging Bragg reflections of high intensity from a small crystal volume were observed. Image-plate diffraction patterns for these two geometries were compared with exposures with equivalent integrated diffracted intensities obtained using a 100 x 100 mum unfocused X-ray beam with the same crystal. The use of the focused beam resulted in a reduction in the exposure time required to produce equivalent patterns by a factor of between 70 and 100.

An eight-position capillary sample spinning stage for the diffractometer at BL20B at the Photon Factory

An eight-position capillary sample spinning stage has been developed for use in conjunction with the versatile vacuum diffractometer (BIGDIFF) at BL20B at the Photon Factory. BIGDIFF is often used in its powder diffraction mode using powders mounted in capillaries and up to eight imaging plates to record the diffraction pattern from the sample. Using the multiple spinning stage a number of diffraction patterns can be recorded on the imaging plates if the imaging-plate cassette is moved behind the Weissenberg screen to a new position after exposure of the sample to the beam. Not only is this system more efficient in terms of time saved in the pumping-down process, but also it has the advantage of allowing the diffraction patterns of standards to be recorded, thereby calibrating both the angle scale of the diffractometer and the intensity scales of the imaging plates absolutely.

Quokka: The Small-Angle Neutron Scattering Instrument

In April 2009, we commenced commissioning experiments on Quokka – the 40 m total flight-path pinhole small-angle neutron scattering (SANS) instrument at the Australian research reactor, OPAL (Figure 1) [1,2].

An energy dispersive time resolved liquid surface reflectometer

Abstract Two designs are presented for an energy dispersive liquid surface reflectometer with time resolution in the milli-second domain. The designs utilise rotating crystal and Laue analyser optics respectively to energy analyse a pink synchrotron X-ray beam after reflection from a liquid surface. Some performance estimates are presented, along with results of a test experiment using a laboratory source and solid state detector.

Time-resolved grazing-incidence diffraction studies of thin films using an imaging-plate camera and focusing monochromator.

A multiple imaging-plate (IP) detector system and focusing monochromator have been developed and successfully applied to the time-resolved study of phase transitions in Langmuir-Blodgett (LB) films by grazing-incidence X-ray diffraction (GIXD). The first reported application of imaging plates to a GIXD study was carried out by our group and proved to be very successful in the determination of thin-film structure [Foran, Peng, Steitz, Barnes & Gentle (1996). Langmuir, 12, 774-777]. To extend the capabilities of this system, an IP camera was designed and built which can accommodate up to 13 IPs (40 x 20 cm) inside the vacuum chamber of the main diffractometer at the Australian Beamline at the Photon Factory. The camera allows the enclosed IPs to be successively exposed and stored inside the diffractometer for later scanning. The focusing monochromator employed in this technique combines fixed exit-beam height with sagittal focusing of the second crystal and delivers a gain in flux of >/=20 times when measured through a 0.1 x 0.1 mm aperture. The utility of the system incorporating the IP camera and the focusing monochromator has been demonstrated through the study of temperature-dependent phase transitions in LB films of metal fatty acids.

Multiple-wavelength powder diffraction using imaging plates at the Australian National Beamline.

The Australian powder diffractometer at the Photon Factory is capable of recording multiple powder-diffraction scans in less than 5 min per pattern using imaging plates in Debye-Scherrer geometry. This, coupled with incrementing the X-ray beam energy in suitably small steps (down to approximately 2 eV) between exposures, allows fast collection of anomalous diffraction data. Data collected from a copper oxide-based superconductor at energies near the Cu K-absorption edge are presented, along with an account of the technique used to extract multiple-exposure powder-diffraction data from imaging plates.