Progress in research and development of mirrors for ITER diagnostics

All optical and laser diagnostic systems in ITER will use metallic mirrors as plasma viewing elements. In the harsh environment of ITER, the performance of mirrors will decrease mainly because of erosion of their surfaces and deposition of impurities. The deterioration of optical properties of diagnostic mirrors will directly affect the entire performance of the respective ITER diagnostics, possibly leading to their shutdown. Therefore, the R&D on mirrors is of crucial importance for ITER diagnostics. There is a coordinated worldwide research and development program supervised by the Specialists Working Group on first mirrors of the International Tokamak Physics Activity, Topical Group on Diagnostics. This paper provides an overview of new results in the field of the first mirrors, covering the manufacturing of ITER mirror prototypes, investigations of mitigation of deposition and mirror cleaning and the predictive modeling of mirror performance in ITER. The current status of research on beryllium deposition a new critical area of mirror research, is given along with an outlook for the future activities.