TEMPERATURE CONTROLLED CHAMBER FOR X-RAY DIFFRACTION SPECIMENS

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A prototype chamber was constructed of polycarbonate and aluminum with a beryllium window to allow the entry of the x-ray beam. The cell containing the specimen is loaded into a holder next to the window. The bottom of the holder is held in contact with one side of a Peltier solid state heat pump. The oppositie side of the heat pump is clamped to the aluminium bottom of the chamber which serves as the heat sink. In this early version, a thermistor was used to control the heat pump to keep the specimen at the set temperature. The film plate is mounted inside the chamber on an adjustable slide. Based on the success of this prototype, two more chambers were requested with different focal lengths. The new units were designed with an improved temperature controller. The new unit incorporates a linear feedback sensor with a bipolar supply to allow automatic switching from cooling to heating. The set temperature is fixed by a 3 digit thumbwheel switch and the sample temperature is read out on a 3 1/2 digit display. This new sytem will hold the sample temperature between -3 degrees C and 85 degrees C with a stability of 0.02 degrees C.