Irradiation test of Mo- and W-mirrors for ITER by low energy deuterium ions

Metallic materials such as molybdenum and tungsten will be used for plasma facing mirrors in ITER. Test pieces of molybdenum and tungsten mirrors manufactured by different methods were irradiated by high flux (5.2–6.0 × 1019 m−2 s−1), low energy (67–80 eV) deuterium ions. The molybdenum mirror manufactured by sintering and electron beam melting of a thin layer of the surface had a higher reflectivity before irradiation than the mirror made without surface melting, but the reflectivity of the former mirror decreased rapidly with fluence. This rapid decrease was caused by blisters generated on the mirror surfaces. The decrease of the 250 nm–20 μm wavelength reflectivity of the molybdenum and the tungsten mirrors made by sintering without surface melting was less than 10% at fluence of 1.2–1.3 × 1025 m−2.