The ITER actively cooled tokamak is the next-generation fusion device that will allow study of the burning plasma over hundreds of seconds. ITER plasma-facing component (PFC) real-time protection will be mandatory to minimize operational risks as water leaks and critical heat flux lead to degradation of PFCs. The protection systems routinely used on Tore Supra (TS) or JET are based on infrared (IR) imaging systems controlling and monitoring the power load on the PFCs through surface temperature measurements. Thanks to TS expertise in actively cooled tokamak and long-pulse operation, three urgent research and development domains are discussed in this paper addressing the feasibility and the performance of the PFC protection function for the new and harsh environment of ITER: (a) the understanding of IR signals in a reflective environment using a physics-based light model simulation; (b) a PFC protection data processing architecture for event detection and identification; and (c) the feasibility, performance, and proto-typing of the first optical component of the imaging systems actively cooled, facing the plasma which will impact the image quality and therefore PFC protection performance.

ITER first mirrors (FMs), as the first components of most ITER optical diagnostics, will be exposed to high plasma radiation flux and neutron load. To reduce the FMs heating and optical surface deformation induced during ITER operation, the use of relevant materials and cooling system are foreseen. The calculations led on different materials and FMs designs and geometries (100 mm and 200 mm) show that the use of CuCrZr and TZM, and a complex integrated cooling system can limit efficiently the FMs heating and reduce their optical surface deformation under plasma radiation flux and neutron load. These investigations were used to evaluate, for the ITER equatorial port visible∕infrared wide angle viewing system, the impact of the FMs properties change during operation on the instrument main optical performances. The results obtained are presented and discussed.

Most of ITER optical diagnostics will be equipped with in-vessel metallic mirrors as plasma viewing components. These mirrors will be exposed to severe plasma environment and must withstand these conditions without change of their optical properties. This implies important research and developments on the design and manufacturing of such components. Therefore, investigations on engineering and manufacturing have been carried out on diagnostic mirrors toward the development of full-scale stainless steel and TZM (Mo-based alloy) ITER mirrors. Several-micrometer coatings of rhodium and molybdenum have been deposited on the components to ensure long-lasting of the mirrors exposed to an environment which could be dominated by charge-exchange neutral flux. Three major issues have been addressed and reported in this paper: First, investigations have been performed on the design and manufacturing of the integrated cooling system to limit the mirror optical surface deformation due to radiations from the plasma and nuclear heating. For the thermomechanical design of the mock-ups, a plasma radiation flux of 0.5 MW/m 2 and a neutron head load of 7 MW/m 3 have been considered. Second, the polishing capability of full-scale (109 mm in diameter) metallic mirrors has been demonstrated: The mock-up surface front error is lower than 0.1 μm root mean square, and the mirrors exhibit low roughness ( Ra <; 2 nm) and low surface defects (scratch width lower than 0.02 mm) after polishing. Third, the manufacturing feasibility of thick molybdenum and rhodium coating layers deposited by magnetron sputtering has been evaluated. The objective of depositing layers up to 3-5 μm thick has been achieved on the mock-ups, with spectral reflectance reaching the theoretical values and showing high reflectivity over a large spectral range (from 400 nm to 11 μm). Finally, the test campaign of the manufactured mirrors, which is being prepared in several European facilities to expose the mirrors to deuterium plasma, ELMs, neutrons, erosion, and deposition conditions, is reported.

Most of the ITER optical diagnostics aiming at viewing and monitoring plasma facing components will use in-vessel metallic mirrors. These mirrors will be exposed to a severe plasma environment and lead to an important tradeoff on their design and manufacturing. As a consequence, investigations are carried out on diagnostic mirrors toward the development of optimal and reliable solutions. The goals are to assess the manufacturing feasibility of the mirror coatings, evaluate the manufacturing capability and associated performances for the mirrors cooling and polishing, and finally determine the costs and delivery time of the first prototypes with a diameter of 200 and 500 mm. Three kinds of ITER candidate mock-ups are being designed and manufactured: rhodium films on stainless steel substrate, molybdenum on TZM substrate, and silver films on stainless steel substrate. The status of the project is presented in this paper.