The reflectivity for neutrons of a plane slab crystal is calculated in the transmission case when the crystal is placed between two Seller collimators. The calculations indicate that the crystal reflectivity, as well as the secondary extinction coefficient, depends signicantly on the angular resolution of the collimators. Curves are given for the extinction of the crystal with different crystal and collimator parameters.
Dietrich, O. W., & Als-Nielsen, J. A. (1965). The effect of Experimental Resolution on Crystal Reflectivity and Secondary Extinction in Neutron Diffraction. Acta Crystallographica, 18, 184-188. https://doi.org/10.1107/S0365110X65000440