Redefinition of Kelvin and the Present Status and Future Prospects of the International Temperature Scale at Low Temperature

Synopsis: The temperature is one of the important parameters, both in experiments and analysis, in cryogenic research and development. Recently the definition of the unit of temperature, Kelvin, which is one of the seven basic units in the International System of Units (SI) was redefined along with three other basic SI units. An outline of the redefinition of the Kelvin and its background are presented. Despite the historic redefinition of the Kelvin, practical cryogenic thermometry is not, and will not be, affected at least for a while. Practical cryogenic thermometry is based on the International Temperature Scales (ITSs). The definitions of the ITSs were not changed after the redefinition of the Kelvin. The relationship between the ITSs and the Kelvin definition, and the characteristics of thermodynamic thermometry are also presented.