Modification of optical properties of Be mirrors under bombardment by deuterium ions

Abstract

Effects of D ion bombardment on Be mirror reflectance, R( λ), in λ=220–650 nm were studied as modelling the impact of charge exchange atoms in a fusion reactor. Without any mass change of mirror, a sharp drop of R( λ) was observed for different kinds of beryllium at high ion energies (600–1350 eV) after ion fluence ∼10 18 ions/cm 2. It is hypothesized that under deuterium ions the BeO surface film was transformed into the Be(OD) 2 film accompanying by changing the film optical properties. Effects of ion energy and ion fluence variation on R( λ) of Be mirror are discussed.