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. 5.3, p. 533


Figure 5.3.3.15
The geometry of the diffractometer used by Fewster & Andrew (1995). The scattering angle, 2ω′, is the fundamental angle for determination of the interplanar spacing and P is the analysergroove entrance. 