Surface temperature measurement of EAST divertor between 20 and 200 °C using the emissivity model prior

Abstract

During the discharge of the Experimental Advanced Superconducting Tokamak (EAST), the divertor target plate (DTP) accumulates a large amount of heat and suffers irreversible damages, so building of a temperature measurement system is crucial for guaranteeing the steady running of EAST. In this work, a radiation thermometer system which mainly consist of a high-speed infrared camera and an endoscope is employed to get surface temperature of upper divertor target plate (UDTP) between 20 and 200 °C. The spectral response function, the geometric factor and the radiation coming from the inner parts of the measurement system are obtained using a reference blackbody placed inside EAST based on multi-temperature calibration method. Meanwhile, in order to reduce temperature measurement error aroused by the emissivity of the divertor material, a nonlinear model is built between 20 and 200 °C in this paper to describe the dependence of spectral band emissivity on temperature. Finally the surface temperature of UDTP is obtained by solving the temperature equation using this emissivity model prior. Based on this method, the surface temperature of UDTP between 20 and 200 °C is measured and it can follow the changes of heating power in EAST real time. Compared with the traditional method in which the emissivity of the divertor material is deemed to a determinate constant, this method can efficiently improve the precision of temperature measurement.