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Figure 5
The beam walk on a non-central crystal is shown for the four possible cases: (a) OA = OAopt, (b) OA = SO, (c) OA > SO, and (d) OA < SO. While the chord SO refers to the central crystal, the beam walk on an outer crystal is given in pink. It is represented by the distance between the impact points on the crystal surface for the operational angles of the detector θo ≤ θ ≤ θf (thick pink line on crystal surface). The minimum, maximum and two intermediate θ angles are shown with the four corresponding Rowland circles (blue circles with the points S, O and A are shown) and the impact points on the non-central crystal (Inθ, pink dots). The centre of the Rowland circle is represented by a green dot (for θo and θf) and the green line depicts its movement over the complete θ range. The non-central crystal is represented by a pink rectangle. The Rowland circle of θm is represented by a black circle. The central inset shows the beam walk in millimetres versus θ for the four cases. The minimum and maximum Bragg angles θo and θf as well as θm are labelled.

Journal logoJOURNAL OF
SYNCHROTRON
RADIATION
ISSN: 1600-5775
Volume 18| Part 6| September 2011| Pages 842-850
doi:10.1107/S0909049511031529
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