The test of Mo and W mirrors under the long-term bombardment by ions of deuterium plasma

The refractory metals are mostly suitable material for fabricating first mirrors for plasma diagnostics in a fusion reactor. Their low sputtering yields under the impact of charge exchange atoms can guarantee long-term mirror operation. An important factor influencing the rate of mirror degradation and reproducibility of results is the structure of its material: monocrystal W and Mo mirrors fabricated of the densest face (110) are shown to have the best characteristic. After mechanical treatment (in the process of monocrystal mirror fabrication), Mo (111) degrades noticeably faster than a perfect monocrystal. The lowest resistance was shown by mirrors fabricated of rolled sheet TZM alloy. The difference in the dependences of reflectance behavior on sputtered depth is explained by microrelief development due to sputtering erosion. In simulation experiments, the sputtering yield was not the only factor influencing the rate of reflectance degradation under bombardment by ions of deuterium plasma. For mirror test data to be reproducible, the material has to be certified; and special precautions should be taken when fabricating mirrors.