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

Comparison of the behavior of Zr(41.2%)Ti(13.8%)Cu(12.5%)Ni(10%)Be(22.5%) amorphous and crystallized mirrors under deuterium ion bombardment

“…The similarity of the changes in reflectance in response to high energy deuterium impact (drop in reflectance) and low energy deuterium impact (recovery of reflectance) to that of Be [16,17] and Al [18] mirrors is consistent with SIMS results which indicate that BeO is the main constituent of the surface oxide layer, see Fig. 4a.…”

“…3; however, this drop in reflectance was nearly fully restored by subsequent exposure to 60 eV deuterium ions (9th exposure in Table 1). This suggests a chemical process similar to that observed for Be [16,17] and Al [18] mirror specimens, where a decrease in reflectance was interpreted as being due to an increase in thickness of an oxide/hydroxide surface layer. The inability of the low-energy deuterium ions to restore the initial (prior to Ar ion exposure) reflectance of this particular specimen confirms that the Ar ions did lead to an increase in surface roughness.…”

“…In previous experiments with the DSM-2 plasma exposure facility where mirror specimens (Be [16,17], Al [18] or amorphous [14]) were exposed to low-energy ions extracted from a deuterium plasma (≤60 eV), the increase in thickness of surface oxide layers has never been observed. On the contrary, when thick oxide/hydroxide layers existed on specimens, the layer would be reduced in thickness by the low-energy deuterium ion exposure.…”

Experimental Simulation of the Behaviour of Diagnostic First Mirrors Fabricated of Different Metals for ITER Conditions

“…In a detailed study on the behavior of Be mirrors exposed to deuterium plasma ions [42,43] it was found that their optical properties strongly depend on the ion energy: with keV energy-range ions a significant drop of reflectance occurs already at relatively low ion fluence (≥5·10 21 ion/m 2 ). After the drop, the reflectance can be fully restored during a much longer time (ion fluence ≥1·10 24 ion/m 2 ) by exposing the mirror to low energy ions (~50 eV) of the same plasma.…”

“…The Be atom supply can be provided due to sputtering of the beryllium surface by deuterium ions that have passed through the oxide film: the higher the D + ion energy, the higher the sputtering rate of the metallic beryllium and the higher the rate of oxide-hydroxide film thickness increase, i.e., the greater the reflectance drop [42,43], Fig. (11).…”