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Figure 2
(a) Geometry of the crystal setting and X-ray and laser illumination. The X-ray beam (red ellipse) probes the volume near the surface of the crystal that is illuminated by the laser light. The laser beam (blue) is substantially larger than the X-ray beam to facilitate alignment. Arrow: positive y′-displacement of the crystal. The region shaded orange shows the new beam position after y′-displacement. The crystal translation along the long axis is 440 µm. The length L is used for the dose calculation. Dashed box: approximation of the beam with a rectangular box. Dotted box: displacement of the box to the new beam position. (b) Model used to determine the common area FC used to calculate the common volume VC. A rectangular X-ray beam (red) whose vertical size is smaller than half the crystal diameter falls on a crystal with a circular cross section. As the crystal is re-oriented by Δθ it is irradiated from another direction (yellow). The orange area is the common area FC that determines the common volume VC. FS is the first term and 2FT the second term in equation (1)[link], respectively (see also the supplementary material). (c) A sequence of angular settings (in degrees). The angular settings are also separated by translations of 22 µm. Five settings are fully or partially exposed given the horizontal size of the X-ray beam. The orange bars denote the relative sizes of the common volumes VC, for each angular setting, values of which are given as a percentage at the bottom.

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