ITER AND FUSION REACTOR ASPECTS THE PROSPECT ON THE USE OF BE MIRRORS IN A FUSION REACTOR WITH BE FIRST WALL

Many methods of plasma diagnostics in a fusion reactor (FR) require the use of so called first mirrors (FM) disposed inside the vacuum vessel. One reason of FM degradation is the deposition on the FM surface of material eroded from the inner components subjected to most intensive plasma impact, i.e., deposition of beryllium in the case of experimental FR (ITER) with Be wall protection. Thus, in ITER only Be mirror can sustain its optical properties for long time and in the present paper results are presented of the simulation experiments on some ITER environment effects on FM made of Be. Namely, effects of bombardment by D ions on reflectance, R(λ), in the λ=220-650 nm range was studied as modelling the impact of charge exchange atoms. It was found that with high ion energy (600-1350 eV) the sharp drop of R(λ), 5-20 %, rising with decreasing wavelength of reflected light, was observed after ion fluence ~10 18 ions/cm 2 . It was supposed that under deuterium ions the BeO surface film was transformed into the Be(OD) 2 film accompanying by changing the refraction and extinction indices of the film, as was registered by ellipsometry measurements. Effects of ion energy and ion fluence variation on R(λ) of Be mirrors are discussed in detail. PACS: 28.52.-s; 52.40.Hf