The half-widths of Bragg intensity profiles measured with a triple-crystal diffractometer at a synchrotron-radiation source. I. Derivation of a simple expression for the full width at half-maximum

On the basis of the expressions given by Rossmanith [Acta Cryst. (1992), A48, 596-610; (1993), A49, 80-91], a simple approximation is derived for the half-widths of Bragg intensity profiles measured with a triple-crystal diffractometer at a synchrotron-radiation source. This new formula facilitates insight into the effects of four parameters - divergence, wavelength spread, mosaic spread and mosaic block size - on the widths of the profiles.