A New Generation of Multicells for Cryogenic Fixed Points at BNM/INM

In January 2000 a European Project called “MULTICELLS” started, in the field of the realisation of low‐temperature standards [1]. In the range from 14 K to 234 K, two competing designs of modular multi‐compartment cells (multicells) for the realisation of low‐temperature fixed points of the ITS‐90 were developed and fabricated by two different partners: BNM‐INM and IMGC [2]. The multicells device allows the calibration, in the same run, of up to three thermometers at all the ITS‐90 triple points in the low‐temperature range, including the mercury point. Several secondary reference points could be optionally added to the system. The limitation of the number of elements is mainly due to thermal effects (thermal homogeneity and response time) and to the dimension of the experimental space of the calorimeter used for measuring the melting curves. In order to reduce the response time, the phase‐transition interface of each element of the multicell containing the substance must be in close thermal contact with ...