Two facilities have been constructed at NIST for realizing and maintaining the ITS-90 below 84 K. The first facility is an integrated low temperature realization system that realizes the ITS-90 below 84 K in its entirety and which we refer to as the Low Temperature ITS-90 Realization Facility (LTRF). The second facility, known as the Low Temperature Calibration Facility (LTCF) is a multi-purpose low temperature facility for scale dissemination and maintenance and for realization of certain ITS-90 triple points in sealed cells. We present a description of the refrigeration, temperature-control, and resistance-measurement systems of the NIST LTRF and LTCF. For the LTRF, we also describe the realization cells and the copper block which contains them, the gas control system, and the pressure measurement system. The comparison and triple-point realization systems of the LTCF are likewise described. The design parameters of NIST fixed point cells as used in both facilities are given. The origin and purity of the NIST fixed-point materials as used in both facilities are given along with the isotopic content in the case of hydrogen.
Proceedings Title: Eighth International Temperature Symposium | 8th | Temperature: Its Measurement and Control in Science and Industry; Volume Seven | AIP
Issue: Pt. 1
Conference Dates: October 21-24, 2002
Conference Title: AIP Conference Proceedings
Pub Type: Conferences
ITS-90, Scale Realization, Temperature, Temperature scales, Thermometry