Magnetically coupled crystal holder and liquid-helium cryostat for X-ray four-circle diffractometer studies between 5 and 300 K

Abstract

A new low-temperature system for X-ray four-circle diffractometer studies down to 5 K has been developed. The crystal is mounted on a new holder which is magnetically coupled to the diffractometer. This coupling is achieved by mounting a master magnet in place of the classical goniometer head. This master magnet drives a slave magnet fixed on the new crystal holder, and therefore the crystal is indirectly oriented by the master magnet. This magnetically coupled crystal holder (MCCH) is enclosed in a helium-flow cryostat which remains stationary during the φ, χ and to movements. The χ value is limited to ±65° and ω to 40° for a 150 mm diameter χ circle. All the tests and data collections (from 5 to 15 d) gave accuracies on the intensities, cell parameters and atomic positions identical to those obtained with a classical goniometer head. No frost problem occurs with this apparatus. The MCCH may also have applications in controlled-atmosphere, high-pressure or vacuum investigations.