Low Temperature X‐Ray Diffraction Apparatus

When studying transformations at sub‐zero temperatures it is often convenient to be able to carry out treatments such as cold‐working and annealing and to transfer the specimen, at temperature, to the x‐ray diffraction camera. Several cameras have been designed, primarily for the x‐ray spectrometer, in which this is easily done. For constant temperature work a flask, having a nozzle which allows cold liquid to flow over the specimen, is used. The holder is such that the specimen can be put in, in correct alignment, while in a cold bath. Two types of cameras giving variable temperatures are described. One, using cold gas blown over the specimen for cooling, permits putting the specimen in place under liquid nitrogen and keeping it at this temperature while it is aligned in the spectrometer. Rapid changes and accurate control in the range up to nearly room temperature are possible. A more versatile camera with a working range from 77°K to over 375°K uses liquid nitrogen as a coolant. Temperature control is by balancing the heat conduction along a tube with a heater near the specimen. This camera allows inserting the specimen at any chosen temperature in the working range but does not allow as rapid temperature changes in the cold gas camera.