Infrared (IR) thermography is a useful diagnostic tool for measuring surface temperatures on divertor plates by using light emitted in the IR range. Japan plans to procure and develop divertor IR thermography for the ITER project. The system design, optical design, and evaluation of detected photons have already been conducted. All optical devices will be installed in the occupied space without interfering with other devices. The required spatial resolution of 3 mm on divertor plates is satisfied by the designed optics. The gamma-ray dose rate at 106 s after shutdown of operations (shutdown dose rate) in the interspace is low (15 - 20 μSv/h). Two color detectors and a spectroscopic system are designed using mirrors with high reflectivity in the range 1 - 5 μm. From the evaluation of detected photons, sufficient photons at 3 and 5 μm can be detected at low emissivity ( ε = 0.2).
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