Long term experience with the “industrial” 3He vapour-pressure thermometer

On the basis of very good experience with a prototype of a 3He vapour-pressure thermometer installed in the magnet feed box (MFB – prototype of LHC magnet test bench), an upgraded version of this thermometer was developed with emphasis on the improvement of its long term stability, reliability and "series" production. The thermometer is working typically around 1.9 K. This article summarises the key points of the prototype design, its upgrade leading to the "industrial/series" realization, the long term experience and the calibration crosscheck of these thermometers after 15 years of operation.