Realization of Helium-4 Vapor Pressure Temperature Scale

摘要

Helium-4 vapor pressure temperature scale between 2.25 K and 4.25 K is realized according to the International Temperature Scale of 1990 by using an absolute pressure transducer. The pressure measurement system is much simpler than the conventional precision pressure measurement system using a pressure balance and a differential pressure transducer simultaneously. Standard-type rhodium-iron resistance thermometers are calibrated against the realized scale. The combined standard uncertainty of the calibration is estimated to be less than 0.1 mK, including the uncertainty of scale realization, resistance measurement, and the residuals of the third-order polynoimial fitting equation.