A cryostat for collection of three-dimensional diffractometer data at liquid helium temperatures

A beryllium-walled cryostat is described which allows collection of nearly a full sphere of accurate three-dimensional X-ray diffractometer data at liquid-nitrogen (LN₂) and liquid-helium (LHe) temperatures. Cryogen consumption is 0.3-0.4 liters of LHe per hour at 30°K and 0.1-0.2 liters of LN₂ per hour at 78°K. The specimen is mounted on a copper block, the temperature of which is controlled to within 0.1°. Measurements with a powder sample of TbVO₄ show that at 33°K the specimen temperature is within 2° of the temperature of the copper block. The cryostat has been used for the collection of several low-temperature data sets. Some special modifications in data-collection and data-processing software are described.