Speaker
Description
Infrared thermography is routinely used for surface temperature measurement of plasma-facing components in tokamaks, but metallic divertor targets introduce uncertainties related to surface emissivity and optical transmission [1]. To improve the temperature measurement capability of the EAST lower divertor, a near-infrared/short-wavelength infrared two-color thermography system has been installed for high-spatial-sampling measurement of the target surface temperature, supporting heat-load assessment, component protection, and future heat-flux reconstruction.
Installed at an upper vertical port, the system integrates a two-color thermometry unit, an endoscopic relay optical system, two short-wavelength infrared cameras, an optical support and alignment assembly, and a data-processing unit. The optical path consists of front imaging optics, relay optics, and rear imaging optics, with a total length of about 3550 mm, a probe diameter of about 60 mm, and a front-end working distance of about 2330 mm. The designed spatial sampling at the target plane is about 0.5 mm/pixel. The cameras have a spectral response range of 400–1700 nm and acquire radiation in two selected bands.
Temperature is reconstructed from the intensity ratio of the two bands according to Planck’s law. Compared with single-band thermography, the two-color method reduces the dependence on absolute radiance calibration, while spectral emissivity effects should be considered [2]. This system provides a new tool for EAST divertor thermography.