The first components are in: perfect single crystals lent to us kindly by the ILL. The Copper ones are made in-house at the ILL and the Germanium ones are available commercially. But then, they are so perfect that they reflect too few neutrons, so the trick is to make them less perfect. At the ILL they are pressed at high temperature to introduce a controlled ‘micro-cracking’. Like that the whole block will consist of many small perfect crystallites that have slight misorientations with respect to the original orientation. This mosaic spread increases the intensity by allowing a larger wavelength band to be reflected. Unfortunately this also increases the divergence of the reflected beam. Typical mosaic spreads are less than a half a degree, although for instance with graphite crystals you can have 2 or 3 degrees.