The visibility of phase indication in n-beam diffraction patterns

[0k0] n-beam diffraction patterns of germanium have been recorded by rotation of specimens about the diffraction vectors of the vanishingly weak 020 and 060, and the very strong 040 reflections. N-beam interactions were displayed clearly in the [020] and [060] scans, and somewhat less clearly in the [040] scan. Unambiguous phase indications, however, were detected only in the [040] scan. The experiments demonstrate that the visibility of n-beam interactions does not necessarily imply a corresponding visibility of experimental phase indications. The geometry of some unusual four- and five-beam interactions detected in the [0k0] scans, and the phases shown by those interactions, are also discussed.