Development and evaluation of the tin point in the ITS-90

Abstract

The freezing point of tin, one of the temperature fixed-points defined in the ITS-90, is newly developed and evaluated. The temperature stability of the furnace is within /spl plusmn/1.5 mK for 24 hours and temperature distribution is within 2 mK over 20 cm. To realize a stable plateau after a large amount of supercooling, the air blow cooling method is introduced instead of the conventional method. The temperature during the plateaus decreases only 0.3 mK for 8 hours and a good repeatability within /spl plusmn/0.026 mK is obtained in ten measurements.