Village: Engineering and Environment
Current Research Techniques:
X-ray powder diffraction
The beamline has three hutches: (i) optics, (ii) experimental hutch 1 and (iii) experimental hutch 2. The optics hutch houses several slits systems, beam diagnostics, monochromator and harmonic rejection mirrors. The primary slits define the white beam produced by the undulator source. Since greater beam stability is achieved by placing a cryogenic monochromator before the mirror for low vertically divergent beams, a double crystal monochromator is the first optical element, located 27.4 m from the source, and gives a fixed exit-height beam geometry requiring no movement of the downstream components each time energy is changed. The mirror assembly provides harmonic rejection of problematic high energy photons that can pass through the monochromator when working at low energies. To cover the required energy range, a double bounce mirror assembly with three stripe surfaces of Si, Rh and Pt element is used.
Experimental hutch 1 (EH1) is approximately 4.0 m high, 9.7 m long, and 5.0 m wide, narrowing to 3.9 m, and houses a large heavy duty 3-circle diffractometer (θ-, 2θ- and δ-circle). Powder specimens in capillary, flat-plate holder or small sample cells can be attached onto a small xyz-table which is mounted on the inner θ-circle. Larger sample cells and stages can be mounted on a large moveable sample table. High sample throughput (200 capillary samples) is available via the robotic arm.
For high resolution measurements, the large 2θ-circle provides scanning of positive angles (above the beam) via the use of 5 multi-analysing crystal (MAC) devices, located around the 2θ-circle with a total of 45 individual Si crystals and photomultiplier based detectors with fast pulse shaping electronics. For time-resolved work a wide-angle position sensitive detector (PSD) based on Mythen-2 Si strip modules mounted on the δ-circle is available. The PSD has been specified to perform fast data collection (e.g. 1 powder pattern/s) with a 90º aperture and angular resolution ~ 0.05º for a 0.7 mm diameter capillary sample.
Experimental hutch 2 (EH2) is approximately 4.0 m high, 7.5 m long and 5.5 m wide and it has been specifically designed for Long Duration Experiments (LDE), where samples require weeks to months of periodically monitoring either ‘slow’ changes or long-term rapid cycling. Data will be collected using a pixel area detector in transmission geometry. There will be a wide range of sample environments available, and the beam size will be 50-200 mm2 at sample. This hutch is currently in the construction phase and we are expecting first users in late 2014.
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