Abstract:
The highly reflective Ag-based thin-film coating for the ITER optical diagnostic mirror was tested under annealing at 250–310$^\circ$C and steam exposure. The Ag grain growth triggered by elevated temperature was identified as the main reason for the deterioration of the coating reflectivity and structure. The SiN$_x$/(SiO$_x$/SiN$_x$)$^2$ nanolaminate barrier composition over the Ag layer was found to effectively suppress the corrosive effect of steam.
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