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![[Figure 3]](nb5369fig3mag.jpg)
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Figure 3
(a) A schematic drawing of the Laue microdiffraction detection geometry at BM32. Five parameters describe the relative position and orientation of the detector with respect to the incoming X-ray beam direction and a point at the sample surface S of the pixelated array (blue). xbet and xgam are two tilt angles usually close to 0°. The distance d separates S from the nearest point N on the detector plane (black), whose coordinates in pixel units are xcen and ycen. For the calibration and the specimen measurements, the sample surface (tilted by ∼40° from the horizontal plane) can be positioned accurately with respect to the microscope objective at a constant reference distance, ensuring the analytical computation of scattering angles of Laue spots coming from S and hitting the detector. (b) The same schematic drawing in the case of an in situ experiment without an optical microscope and with thermal drift of the sample surface. Without the microscope and due to the vertical thermal dilation of the sample along ZS (red arrows), Laue spots originate from S′ and new calibration parameters must be used. If xbet = xgam ≃ 0 and the sample surface does not rotate significantly, only the value of ycen is modified (blue arrow, see main text). |
![[Figure 3]](nb5369fig3.jpg)
 | JOURNAL OF APPLIED CRYSTALLOGRAPHY |
ISSN: 1600-5767
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