Technique for determining the orientation of single crystals of bismuth

Except in particular cases, neither X-rays nor light figures alone suffice to determine completely and unambiguously the orientation of a bismuth crystal rod. The technique described consists of a combination of the two. The light figure pattern is used to locate the (111) plane approximately in order to aline the rod relative to the X-ray beam before the back-reflexion Laue photograph is taken, and to assist in the interpretation of the stereographic projection. The modifications made to a Unicam single-crystal X-ray goniometer to enable the technique to be applied to rods of 6 mm diameter and 25 cm length are described.