Some peculiarities in the behavior of Be surfaces under bombardment by ions from a deuterium plasma

In experiments with Be mirrors bombarded by keV ions from a deuterium plasma a sharp drop of reflectance in the wavelength 220–650 nm was observed after quite low ion fluence although no mass loss of Be sample was measurable. Therefore such change of reflectance was ascribed to the transformation of the oxide layer, that naturally coats the Be mirror, into a hydroxide film. Supporting this hypothesis, the vacuum annealing of exposed samples at elevated temperature resulted in partial restoration of the reflectance. The effect of deuterium ion bombardment was closely related to the ion energy: the higher energy the deeper the drop of reflectance. In the paper we present results on the reflectance of Be mirrors depending on the experimental conditions, i.e., on the ion energy, annealing temperature, duration of exposure to bombardment by deuterium ions.