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Effects of gamma radiation on optical coating materials for highly reflective space mirror
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DOI：10.1016/j.asr.2026.03.066.png)
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Abstract
En 中文
Optical components in telescopes and satellites often rely on silver mirrors to enhance sensitivity. However, without protective coatings, these mirrors are prone to oxidation and sulfurization, which degrade their performance over time. For space applications, it is crucial to investigate the impact of space radiation on the physical and chemical properties of these coating materials. This study utilizes physical vapor deposition (PVD) to deposit a variety of oxides on glass substrates, including silica (SiO2), alumina (Al2O3), yttria (Y2O3), hafnia (HfO2), tantalum pentoxide (Ta2O5), niobium pentoxide (Nb2O5), and titania (TiO2). Highly reflective silver mirrors in the visible region were also fabricated by coating silver with some materials. To simulate the total accumulated gamma (c) radiation dose that observational satellites might experience during long-term exposure in low Earth orbit, all samples were irradiated using a cobalt (Co)-60 source with doses ranging from 5 to 40 krad. Changes in the refractive index, extinction coefficient, and bandgap energy of the thin oxide films and coated silver mirrors after exposure to high-energy radiation were analyzed using a spectrometer, an ellipsometer, and the Tauc plot method. The results revealed that irradiation caused increased extinction coefficients and decreased refractive indices in dielectric materials, with HfO2 and Ta2O5 showing the highest radiation stability and TiO2 the least. Metallic films (Ag, Al, Bi) remained stable under gamma exposure. Multilayer silver mirrors showed minor reflectance changes, attributed to TiO2 degradation or SiO2 protective layer effects. Among various glass substrates, B270 suffered significant discoloration, fused silica showed excellent resistance, and S-BSL7R and BK7G18 experienced minimal ultraviolet (UV) absorption shifts. (c) 2026 COSPAR. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Keywords:
Silver mirror
Enhanced silver coating
Gamma (c) radiation
Low Earth orbit (LEO) satellite
Space optics
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