Emissivity measurement of tungsten based on a double-wavelength infrared thermometer between 140 and 500℃

Abstract At present, most Tokamak devices adopt non-contact temperature measurements for the first wall using an infrared thermometer. Tungsten is regarded as the most likely plasma-facing material, especially as the divertor target, in future Tokamka devices. Accordingly, it is important to obtain accurate emissivity of tungsten for accurate temperature measurement of the divertor target plate and ensuring steady operation of Tokamak devices. In this work, a set of emissivity measurement equipment with a self-designed double-wavelength colorimetric infrared thermometer is established, and a method of emissivity measurement based on double-wavelength colorimetry considering background radiation is proposed. The normal spectral emissivity of tungsten with wavelengths of 10.2 μm and 10.8 μm between 140 and 500℃ in the same working environment as the Tokamak devices is measured after calibrating the optical splitter and the infrared thermometer by using a blackbody furnace. The measurement results indicate that the normal spectral emissivity of tungsten ranges from 0.0936 to 0.1246 between 140 and 500℃ in a vacuum environment. The emissivity increases with the increase of temperature, and the relative increase rate is 33.12%. Finally, the uncertainty of the emissivity measurement results is calculated, which ranges from 0.0444 to 0.0767. The normal spectral emissivity of tungsten measured based on the double-wavelength colorimetric principle proposed in this paper provides a good reference for the accurate temperature measurement of the divertor target plate in Tokamak devices. It also provides a reference for the measurement of metal emissivity with background radiation under similar vacuum conditions.