International
Tables for Crystallography Volume C Mathematical, physical and chemical tables Edited by E. Prince © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. C. ch. 2.3, p. 48
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The projected source width and receiving-slit width RSw each add a symmetrical broadening to the profiles that is constant for all angles. Both the profile width and the intensity increase with increasing take-off angle (Section 2.3.5
). However, the contribution of
is small when the line focus is used, Fig. 2.3.1.9(a)
. The receiving slit can easily be changed and it is one of the most important elements in controlling the profile width, intensity, and peak-to-background ratio, as is shown in Figs. 2.3.1.9(a) and (c)
. Because of the contributions of other broadening factors, αRS can be about twice αF (line focus) without significant loss of resolution.
The projected width of the X-ray tube focus is given in equation (2.3.1.2
). The aperture is
For a line focus with actual width
= 1 mm, ψ = 5°, and R = 185 mm, αF = 0.011°. The receiving-slit aperture is
For RSw = 0.2 mm and R = 185 mm. αRS is 0.062°. The FWHM of the profiles is always greater than the receiving-slit aperture because of the other broadening factors.