低温における比熱容量標準の整備

抄録

Specific heat capacity is one of the most important thermodynamic properties for materials. In the National Metrology Institute of Japan (NMIJ), we have developed a new type of cryogenic adiabatic calorimeter applying a pulse-tube (PT) refrigerator for specific heat capacity standards. By using the PT refrigerator and a digital PID control system, the calorimeter realized easy and safety operation, full automation, and continuous long-term operation. In the first step, we measured the specific heat capacity of NIST SRM720,¹⁾ synthetic sapphire, in order to check the performance of the equipment and estimate the uncertainty of measurement. In the next step, we measured the specific heat capacity of a single-crystalline silicon. Certified reference material (CRM) for the specific heat capacity was produced in accordance with the quality system of NMIJ, which is in compliance with ISO Guide 34 and ISO/IEC 17025. In this paper, we discuss the development of a standard and CRM for specific heat capacity at low temperatures.