Irradiation of KU1 and KS-4V substrate SiO₂ overcoated Al mirrors

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• 作者：Piedad Martin ; Teresa Hern ; ez ; Andrei Goussarov ; Eric R. Hodgson ; Andrey M. Litnovsky ; Mario Di Fino ; Francesco Orsitto
• 关键词：Dielectric mirrors ; Reflectivity ; X-ray photoelectron spectroscopy (XPS) ; Irradiation effects
• 刊名：Fusion Engineering and Design
• 出版年：2013
• 出版时间：October, 2013
• 年：2013
• 卷：88
• 期：6-8
• 页码：1224-1227
• 全文大小：535 K

文摘

Previous work on overcoated dielectric mirrors identified several radiation problems; UV-visible reflectivity degradation, unreliability of manufacturers coating specifications, and conversion of SiO coatings to SiO₂ leading to swelling and cracking, and hence possible corrosion during LOCAs (loss of coolant accident). We report the results obtained for gamma and neutron irradiation of prototype mirrors with KU1 and KS-4V high purity silicas replacing the standard Pyrex substrate to overcome the problem of activation due to high impurity content. To avoid the SiO to SiO₂ conversion problem, the Al layer has been overcoated with SiO₂. The mirrors show high reflectivity (>80 % ) down to 200 nm. After gamma irradiation at 170 ¡ãC in a dry nitrogen atmosphere to 10 MGy, no degradation in reflectivity was observed. They were then neutron irradiated in vacuum at 35 ¡ãC to 6.8 ¡Á 10¹⁶ n/cm² (fast fluence) and reflectivity examined with a specially designed spectrometer system with a remote integrating sphere for hot cell use. Again no degradation in reflectivity was observed.