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Figure 5
Numerical calculation (purple curve) of the beam profile expected to be projected onto the detector line on an instrument as compared with an actual measurement (points with error bars which represent ± one standard deviation and a corresponding confidence interval of approximately 68%). The computed curve is not a fit but only scaled to the measured intensity. This calculation takes into account the affect of the geometrical angular divergence (defined by the pair of slits) on a summation of diffracted intensity patterns from the second slit downstream – as predicted by the standard Fraunhofer diffraction formula for multiple source points across the width of the first (upstream) slit. Another calculation, corresponding to what would be expected based on a consideration of geometrical ray optics alone (blue curve), is also plotted. The agreement in the case in which both geometrical and diffraction effects are included is markedly better.

Journal logoJOURNAL OF
APPLIED
CRYSTALLOGRAPHY
ISSN: 1600-5767
Volume 55| Part 4| August 2022| Pages 787-812
https://doi.org/10.1107/S160057672200440X
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