A novel X-ray precession goniometer for use with stationary single crystals in special enviroments. Adaptation of a closed-cycle refrigerator

A unique single-crystal X-ray precession goniometer suitable for studies that require special environments (cryostat, pressure cell, magnet) is described. The precession motion is transferred to the incident beam by means of a double-crystal monochromator in such a manner that the sample remains at rest and the motion of the film (or other area detector) is simplified. This versatile instrument allows the adaptation of complex or cumbersome apparatus; that of a closed-cycle refrigerator is presented as an example. The capability of the X-ray goniometer is illustrated with low-temperature precession photographs for RbC₂₄ and (TMTSF)₂ClO₄ (TMTSF = tetramethyltetraselenafulvalene).