D2B - High-resolution two-axis diffractometer
D2B - High-resolution two-axis diffractometer
D2B is very high-resolution powder diffractometer designed to achieve the ultimate resolution, limited only by powder particle size (Δd/d 5x10-4), but is was built so that an alternative high flux option, with resolution comparable to that of D1A, but much higher intensity, could be chosen at the touch of a button.
Applications
- The structural chemistry of non-rigid molecules
- Ab-initio structure solution from powders
- Crystal and magnetic structure determination of powder compounds (even small samples)
- Dependance in temperature/pressure/magnetic field structural (or magnetic) studies for powders
Instrument layout
D2B seen from behind the detector, i.e. from the opposite of the normal access to the experimental area.
A general view
The diffractometer D2B is characterised by the very high take-off angle (135°) for the monochromator, which has a relatively large mosaic spread of 20’ to compensate for the corresponding intensity (Δl/l) loss. It is 300 mm high, focusing vertically onto about 50 mm; this large incident vertical divergence is matched by 200 mm high detectors and collimators.
A complete diffraction pattern is obtained after about 100 steps of 0.025° in 2θ, since the 64 detectors are spaced at 2.5° intervals. Such scans take typically 30 minutes; they are repeated to improve statistics.
The sample changer of D2B
The automated sample changer makes it possible to measure several samples without human action. This can accomodate sample environment devices such as one or more liquid helium cryostats as shown on the instrument layout.
The set-up used for magnetic studies
Here D2B is shown with a 5 Tesla cryomagnet installed on the sample table.