Evaluation of transfer standard platinum resistance thermometers using pressure-controlled cesium heat pipe

A comparison furnace using a pressure-controlled cesium heat pipe was developed and its characteristics were investigated experimentally. The heat pipe has five wells by which five platinum resistance thermometers can be compared simultaneously. Good temperature stability of 0.078 mK was achieved at 660/spl deg/C and good temperature uniformity of 0.28 mK over a zone of 4 cm was obtained at 520/spl deg/C. Using this furnace, thermometer comparison at the uncertainty of 1 mK or so in the range from 395/spl deg/C to 660/spl deg/C can be expected. Transfer standard platinum resistance thermometers, which have been developed in our laboratory, would be compared with an ordinary standard platinum resistance thermometer to evaluate their characteristics.