Reflections and surface temperature measurements in experimental fusion reactors Tore-Supra, JET and ITER

In nuclear fusion experiments with water cooled plasma facing high heat flux components as in Tore Supra and ITER, infrared thermography is and will be used to survey their temperature during operation to avoid damage. The use of metallic components makes things more difficult for surface temperature measurements because of reflections. This paper deals firstly with the estimation of errors made on surface temperature measurements on these high heat flux plasma limiters (first material objects limiting the radial extension of the plasma) due to multiple reflections of the light from the limiter back to the limiter itself, and secondly with specular/diffuse reflections on the main limiter, from other hot elements of the machine. Both effect are small in machines with high absorption (carbonaceous) limiters but quite important in machines with reflecting (metallic) limiters.