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Figure 2
Experimental geometry for grazing-incidence scattering experiments. (Left) An incident X-ray beam (black) is refracted upon entering a thin film, and further refracted upon entering the substrate. Thus, the transmitted beam (blue) is shifted relative to the direct-beam position. Scattered rays (purple) are also refracted as they exit the film. As a result, a scattering event (purple ring) occurring with angle [2\alpha _{\rm s} = \alpha _{\rm i} + \alpha _{\rm f}] in the sample's reciprocal space (Q) is observed at a different apparent scattering angle ([2\theta _{\rm s} = \theta _{\rm i} + \theta _{\rm f}]) and therefore experimentally measured on the detector at a different reciprocal-space coordinate (q). (Right) An example GISAXS image, with the qz positions noted for the transmitted beam (T), the horizon (H), the Yoneda (Y) and the specular reflected beam (R).

IUCrJ
Volume 5| Part 6| November 2018| Pages 737-752
ISSN: 2052-2525
https://doi.org/10.1107/S2052252518012058