International
Tables for
Crystallography
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

International Tables for Crystallography (2006). Vol. C. ch. 2.5, p. 84

Figure 2.5.1.1 

B. Burase and L. Gerwardb
[Figure 2.5.1.1]
Figure 2.5.1.1

Standard and conical diffraction geometries: 2θ0 = fixed scattering angle. At low scattering angles, the lozenge-shaped sample volume is very long compared with the beam cross sections (after Häusermann, 1992[link]).