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The minimum scan range and detector aperture as a function of specimen size in X‐ray diffractometry
Author(s) -
McL Mathieson A.
Publication year - 1984
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889884011304
Subject(s) - optics , crystal (programming language) , aperture (computer memory) , diffraction , detector , beam (structure) , scattering , angular aperture , range (aeronautics) , physics , x ray , materials science , focal length , lens (geology) , computer science , acoustics , composite material , programming language
The theoretical functional relationship of scan range and detector aperture to (spherical) crystal size in respect of scattering angle θ in X‐ray diffractometry for different scan modes is not clearly defined in the literature. It is shown that it is necessary to examine separately the factors determining the angular apertures of the beam incident on the crystal and of the beam diffracted from the crystal, and then the appropriate relationship is derived for a point source and a small spherical crystal for the ω ‐scan mode. The required aperture is shown to be 2 a c cos 2 θ , where a c is the diameter of the crystal. Using ( Δω , Δ 2 θ ( s ) ) component diagrams [Mathieson, (1983). Aust. J. Phys. 36 , 79–83], the corresponding results are derived for the ω/θ ‐ and ω /2 θ ‐scan modes and the three results are shown to be consistent with the earlier deductions which yielded cos 2 θ for the ω ‐scan mode but not with those which yielded cos θ .