Laue-Laue monochromator

Energy selection at ID11 can be achieved using the double bent Si(111) crystal monochromator that operates in a horizontal Laue geometry allowing the band pass to be matched to the specific needs of an experiment. The crystals are bent to match the Rowland circle geometry so that all rays of a divergent white beam incident on different parts of the crystal are reflected with the same angle, preserving the source properties. The band pass of the monochromator crystal is then defined by the crystal thickness (2.5 mm), the asymmetric cut (12.5^o) and the bending radius.