Study of the normal spectral emissivity of tungsten between 170 and 500 °C by a single-wavelength infrared thermometer

Abstract Tungsten is considered as the potential plasma facing material in future fusion reactors due to its high melting point, low sputtering, and low fuel retention, and is already used as the baseline material for divertors in some Tokamak devices. The emissivity of tungsten is low and varies with the target temperature, surface state, and wavelength, etc. Therefore, it is indispensable to obtain the emissivity characteristics of tungsten for accurate temperature measurement in the Tokamak devices. In this work, the emissivity measurement system using a single-wavelength infrared thermometer with the same operating conditions as Tokamak devices is constructed and the normal spectral emissivity of tungsten between 170 and 500 °C is measured. The measurement results indicate that the normal spectral emissivity of tungsten ranges from 0.0880 to 0.1291 between 170 and 500 °C with the wavelength of 10.2 μm, and the emissivity increases with the increase of temperature. Meanwhile, the uncertainty of emissivity measurement results is estimated, which ranges from 0.0064 to 0.0125. Besides tungsten, the proposed emissivity method can also be applied to measure the emissivity of other first wall materials such as molybdenum, etc. This work provides a useful reference for accurate temperature measurement of the first wall in nuclear fusion devices.