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Beamline: F3
High Pressure Powder Diffraction
This station receives the white beam from a bending magnet and is optimized for energy-dispersive powder diffraction. It is especially geared for work with high pressure diamond anvil cells. Because of the small sample sizes involved in this work, the equipment has been optimized for background suppression (including the use of long He-flushed beam pipes), generation of small and well-defined beam sizes down to 20 x 20 µm (produced by two tungsten collimators, one of which in a gimbal-type holder), and rapid alignment (using a He-Ne laser, ionization chambers, photodiodes, scintillator screens and a video system).
For energy-dispersive X-ray diffraction, there is a Ge detector (with a resolution of about 1%) for scattered radiation in the horizontal plane at angles up to 2 θ = 30°. An adjustable double-slit system serves to reduce the Compton scattering from the diamonds and improves the resolution. This system rotates with the detector and allows for rapid changes in the diffraction angle.
A Huber diffractometer serves for sample translation, rotation and tilting, and for detector alignment (angle changes) in the energy-dispersive mode. The precision of the translations is below 1µm, that of the rotations and tilts 0.5 millidegrees. It can accept (centered) loads up to 80 kg (such as ovens and cryostats). Control is via a manual controller via a standard CAMAC crate.
Ancillary optical equipment can be set up on an optical table around the diffractometer. An on-line facility for pressure measurement via the ruby fluorescence method and a laser-heating facility are being set up.
A PC coupled to a multi-channel analyzer is used for data collection and storage in the energy-dispersive experiments.
There is an off-line facility for pressure determination with the ruby fluorescence method. This room is also used for sample preparation. It is equipped with a stereo microscope, a device to measure the thicknesses of gaskets, a drilling machine for gaskets, and a glove-box.
Applications
(Micro) diffraction at variable temperature and pressure (8 < T < 4000 K, 0 < P < 2 Mbar)
Structure determination and investigation of phase transitions
Study of kinetic phenomena
Literature on Instrumentation
J. Staun Olsen, B. Buras, L. Gerward and S. Steenstrup, J. Phys. E: Sci. Instrum. 14 (1981) 1154
R. Boehler, N. von Bargen and A. Chopelas, Jour. Geophys. Res. B95 (1990) 21731
J.W. Otto, HASYLAB Jahresbericht 1993, p. 931
Instrument Specification
|
Source (4.5 GeV) |
bending magnet, Ec = 16 keV |
|---|---|
|
Beam Characteristics |
white beam |
|
Beam Characteristics |
< 0.2 mm (adjustable) |
|
Detector |
Ge (solid state) |
|
Angular range |
0 < 2θ< 30° (horizontal only) |
|
Energy resolution |
Δd/d = 10 x 10-3 above 26 keV |
