Comparison of the Triple-Point Temperatures of ~(20)Ne, ~(22)Ne and Normal Ne

摘要

At the National Metrology Institute of Japan (NMIJ), the triple points of ~(20)Ne and ~(22)Ne were realized using modular sealed cells, Ec3Ne20 and Ec8Ne22, made by the Istituto Nazionale di Ricerca Metrologica (INRiM) in Italy. The difference of the triple-point temperatures of ~(20)Ne and ~(22)Ne was estimated by using the sub-range of standard platinum resistance thermometers (SPRTs) calibrated by NMIJ on the International Temperature Scale of 1990 (ITS-90). The melting curves obtained with the Ec3Ne20 and Ec8Ne22 cells show narrow widths (0.1 mK) over a wide range of the inverse of the melted fraction (1/F) from 1/F=1 to 1/F=10. The liquidus point T_(tp) estimated by the melting curves from F～0.5 to F～0.85 using the Ec8Ne22 is 0.146 29 (4) K higher than that using the Ec3Ne20 cell, which is in good agreement with that observed by INRiM using the same cells. After correction of the effect of impurities and other isotopes for Ec3Ne20 and Ec8Ne22 cells, the difference of T_(tp) between pure ~(20)Ne and pure ~(22)Ne is estimated to be 0.146 61 (4) K, which is consistent with the recent results reported elsewhere. The sub-ranges of SPRTs computed by using the triple point of ~(20)Ne or ~(22)Ne realized by the Ec3Ne20 cell or the Ec8Ne22 cell in place of the triple point of Ne for the defining fixed point of the ITS-90 are in good agreement with those realized on the basis of the ITS-90 at NMIJ within 0.03 mK, which is much smaller than the non-uniqueness and the sub-range inconsistency of SPRTs.