During the last decade, laser thermometry has become a powerful tool for measuring the temperature of gases without contact. The use of a laser allows non-intrusive access to gaseous media, even under extreme conditions, and the measurements offer high spatial and temporal resolution. It is a fast evolving technology, which is important in a large field of scientific and industrial applications. However, traceability of the measurements to the international temperature scale has not been achieved.
The aim of the project was to develop a transfer standard for laser thermometry (TSL) in gases in the temperature range from 50°C to 1600°C which will constitute the basis for traceability of laser thermometry to the International Temperature Scale of 1990 (ITS-90). The transfer standard will be used for investigations on the accuracy of coherent anti-Stokes Raman scattering (CARS) thermometry. Different sources of inaccuracies of broadband and scanning CARS will be investigated. A description of the calibration of CARS laser thermometry will be developed.
The transfer standard for laser thermometry has been designed and constructed. The standard provides optical access to a sample volume of gas maintained at a stable ((0.3%) temperature within the range of 25°C to 1600°C. The gas temperature is measured using built-in, calibrated thermometers including thermocouples, AccufiberTM optical-fibre probes and an optical pyrometer for traceability to the ITS-90. Broadband Coherent Anti-Stokes Raman Scattering (CARS) and scanning CARS experiments have been performed inside the furnace. The influences of apparatus function, non resonant susceptibility, background noise, spectral behaviour of the Stokes laser beam and saturation effects have been determined. The deviation between CARS temperature evaluation and the temperature indicated by the TSL thermometers for temperatures higher than 1070 K is smaller than 2%. For lower temperatures the deviation increases up to 12%. The uncertainty for broadband CARS temperature evaluation at 777K is smaller than 1%, the reproducibility is 0.4%. For scanning CARS the uncertainty is larger. At 1200K the uncertainty is 2% and the reproducibility is 2.6%. A description for the calibration of CARS thermometry has been worked out.
Christof Rieck 1/1
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Construction of a furnace in order to heat a gas volume to a defined temperature (NPL).
Selection, calibration and installation of conventional thermometers for the traceability to the ITS-90 (PTB).
Scanning and broadband CARS experiments within the TSL in order to proof the features of the furnace and the accuracy of CARS (ONERA, ILT).
Investigations on sources for inaccuracies of CARS thermometry (ONERA, ILT).
Description of a calibration procedure for CARS (ONERA, ILT)
Funding SchemeCSC - Cost-sharing contracts
TW11 0LW Teddington