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Figure 1
(a) Schematic of the experimental geometry at the 34-ID-C beamline. Rotations in (a) are shown at one diffractometer snapshot; when the sample stage is rotated to θ = 0°, φ = 0° and χ = 90° and the BCDI detector is rotated to γ = 0°, δ = 0°. At θ = 0°, the incident beam is perpendicular to the detector surface when the detector is sitting at δ = 0° and γ = 0°. At χ = 90° and φ = 0°, the surface normal of the sample is parallel to the y-axis. The diffractometer is as specified in the Spec Sixc mode (Vlieg, 1997BB44). The incident X-ray beam is antiparallel to the z-axis of the laboratory frame. The Laue detector is shown with its surface being normal to the x-axis of the laboratory frame; the x-axis points towards the outboard of the synchrotron. The BCDI detector sits at the end of an arm and has three degrees of freedom, the detector distance and the angles γ, δ, as shown. The origin is located at the center of rotation of the diffractometer within a couple of micrometres. (b) Schematic of the two Bragg peak measurement for the detector calibration. The two Q vectors correspond to two separate measurements. For the first measurement the crystal is oriented so that the monochromatic beam diffracts from the (111) atomic planes. The intensity of the (111) Bragg peak, which is recorded by the BCDI detector, is optimized by tuning the θ, φ, χ angles of the sample stage. Then a Laue pattern is collected at the exact position after switching to the pink beam. The same process is repeated for measuring the 022 Bragg peak and the corresponding Laue pattern at the given position. All coordinate systems are right-handed.

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ISSN: 1600-5775
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