Precision determination of lattice parameters at low temperatures without the use of liquid gases

The design of a vacuum jacketed multiple-exposure back-reflection camera and the adaptation of this camera to a closed circuit pressurized helium cryostat has made it possible to determine lattice parameters by X-ray diffraction to temperatures as low as 25 °K without liquid gases. The advantages of this new design are: short exposure periods (5 to 30 minutes), multiple (usually 6) exposures on a single film at any temperature between 25 and 180 °K, elimination of film shrinkage and hence, high precision lattice constants and thermal expansion coefficient determinations; easy detection of phase transformations. The lowest temperatures can be reached in 30 minutes.