High-resolution two-axis diffractometer

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.