Development of a transfer standard for laser thermometry

The measurement of gas temperatures is important in many combustion, chemical manufacturing and materials processing applications. Different laser spectroscopic methods are applied to measure the temperature of gases. Nevertheless, up to now none of these methods have been calibrated against the international temperature scale of 1990 (ITS-90). A transfer standard for laser thermometry (TSL) has been developed to calibrate laser thermometry techniques. The standard provides optical access to a sample volume of a gas maintained at a stable temperature within the range of 300 K to 1850 K. The gas temperature is measured using built-in, calibrated thermometers including thermocouples, Accufiber 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 measuring uncertainty of broadband CARS amounts to less than 4 per cent between room tempera ture and 800 K. At temperatures between 800 K and 1850 K an uncertainty of less than 2 per cent has been achieved. For scanning CARS the uncertainty and the precision amounts to 2 per cent between 295 K and 1850 K.