29th Symposium on Fusion Technology (SOFT 2016)

P1.071 Measurement of surface temperature of the plasma facing component with Multi-Spectral Infrared thermography diagnostics

5 Sep 2016, 14:20

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 71

Poster D. Diagnostics, Data Acquisition and Remote Participation P1 Poster session

Speaker

Chen Zhang (Cadarache Center)

Description

For the long-pulse high-confinement discharges in future tokamaks, the equilibrium of plasma requires an interaction and energy exchange with the first wall materials. The heat flux resulting from this interaction is of the order of 10 MW/m²2 for steady state conditions and up to 20 MW/m² 2 for transient phases. As a result, surface temperature measurement of the plasma facing components (PFCs) up to more than 3000°C is a major concern to ensure safe operation of large fusion facilities. In tokamaks, infrared (IR) thermography systems are routinely used to monitor the surface temperature of the PFCs. This measurement requires an accurate knowledge of the surface emissivity. To solve this problem, a multi-spectral infrared measurement is proposed as a promising solution. The system has the advantage to carry out a non-intrusive measurement on thermal radiation whilst evaluating surface temperature without requiring a mandatory surface emissivity measurement. In this paper, a conceptual design for the multi-spectral infrared thermography is proposed for detection wavelengths range from 1.5 to 5 mm. The numerical study of the multi-channel system based on the Levenberg-Marquardt (LM) nonlinear curve fitting is applied. The optimization for system wavelength choice is presented. The numerical results presented in this paper demonstrate that this method allows for measurements up to 3000°C with a relative bias of 10%. Furthermore, laboratory experiments have been performed from 200 °C to 740 °C to confirm the feasibility for temperature measurements on stainless steel and tungsten with emissivity variation from 0.1 to 0.4. In the experiment, most of the unfolding results from the multi-channel detection provide a relative bias of 5% below 740 °C, which agrees with theoretical analysis and demonstrates the feasibility for metallic surface temperature measurement with this technology.