A Concerted International Project to Establish High-Temperature Fixed Points for Primary Thermometry

Abstract

Research into high-temperature fixed points above 1,100 • C has made significant progress since they were first reported in 1999. In particular, it has been established that single cells are repeatable at the sub-50 mK level, and intra-cell reproducibility at the 100 mK level has been demonstrated even at temperatures as high as 2,500 • C. The fixed points have been used to compare temperature and radiometry scales over a wide temperature range, and are being developed and established as secondary references for thermocouple calibrations. However, before they can be fully accepted as primary temperature references, much work remains to be done, namely:(1) Establishment of long-term stability of the fixed-point temperature; (2) Development of robust procedures for the reliable construction of the fixed-point cells (to ensure routine intra-cell reproducibility of 100 mK); (3) Demonstration of long-term robustness of the fixed-point cells; (4) Assignment of thermodynamic temperatures to a selected set of fixed points; (5) Agreement and acceptance of these temperature values by the CCT; (6) Agreed methods on how to take full utility of these new fixed points into any future International Temperature Scale (ITS)-or the current ITS-90

Experimental assessment of methods of dissemination of the thermodynamic temperature at the highest temperatures

“…The InK project [3,4] contains four technical work packages with the following objectives/work packages, including activities already planned in a concerted international research project [5]:…”

Erratum to: Experimental assessment of thermodynamic temperature dissemination methods at the highest temperatures

“…The InK project [3,4] contains four technical work packages with the following objectives, which include activities already planned in a concerted international research project [5]:…”

Reducing uncertainty in practical radiation thermometer calibration based on proposed changes to themise en pratiqueof the definition of the kelvin

“…The P715 thermometer was calibrated at fixed points of cobaltcarbon (nominally 1324 °C), platinum-carbon (1738 °C) and rhenium-carbon (2474 °C). Two uncertainty budgets were prepared: one using target uncertainties for current research [3] of 0.2 °C at the cobalt-carbon point, 0.3 °C at platinum-carbon and 0.4 °C at rhenium-carbon, and one using the uncertainty when assigning temperatures using current ITS-90 capability. The uncertainty budget components in assigning a temperature and signal at each fixed point are based on the Comité consultatif de thermométrie (CCT) recommendations [5] and the propagation of the uncertainties between fixed points follows [6].…”

“…These could be used to directly calibrate a transfer standard, bypassing the primary standard and variable temperature blackbody route. To assess the potential benefits to a calibration laboratory a simple and relatively low cost radiation thermometer was calibrated using high temperature fixed points with an uncertainty budget based both on the expected outcome of current Tassignment measurements [3], and also on current ITS-90 capability. This thermometer was then used at LII to determine the uncertainties that might be achievable in assigning a temperature to their blackbody source in comparison to the current route.…”