First mirror issues and measures for harsh environment of ITER

Sugie, Tatsuo; Ogawa, Hiroaki; Iwamae, Atsushi; Kawano, Yasunori; Hatae, Takaki; Kajita, Shin*; Kusama, Yoshinori

Plasma facing first mirrors of ITER will experience relatively higher levels of radiation due to neutron, ray irradiation than in present devices. An additional potential damaging effect for the first mirrors is the formation of coatings of impurities, such as Be, W, C, etc. due to erosion and re-deposition of the materials of the first wall and the divertor. Issues of the first mirror are summarized and the total fluxes and energy distributions of deuterium, helium, carbon and deuterium molecule at the first mirror positions are estimated. Protective and mitigating measures to minimize the degradation of first mirror reflectivity are adopted in the system designs of diagnostics. However, the reflectivity may change due to the environmental effects. An in-situ and remote sensitivity calibration system withstanding in the strong radiation field has been developed. Finally, remaining issues are summarized.