D2B - High-resolution two-axis diffractometer

D2B is a very high-resolution powder diffractometer designed to achieve the ultimate resolution (limited only by powder particle size, Δd/d 5x10^-4). The instrument is built in such a way that an alternative high flux option (with resolution comparable to that of D1A but much higher intensity) can be chosen at the touch of a button.

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.

D2B seen from behind the detector, i.e. from the opposite of the normal access to the experimental area.

Automated sample changer©2009, ILL, E. Suard & L. Gendrin - 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.

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