³He Vapour‐Pressure Measurements at PTB

The paper reports on extensive ³He vapour‐pressure measurements carried out at PTB. To investigate in detail the main error sources, three different types of vapour‐pressure cells and three different arrangements of pressure‐sensing tubes were used. In the temperature range from 0.65 K to 1.2 K, the repeatability of the realisation of ³He vapour‐pressure temperatures T₉₀ according to the International Temperature Scale of 1990, ITS‐90, over eight runs was of order of 0.12 mK, whereas the repeatability over four runs using one and the same, optimised cryogenic set‐up was of order of 0.03 mK. Below 1 K, the T₉₀ realisation is compared to data available in the literature via wire scales.