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Life prolongation of far ultraviolet reflecting aluminum coatings by periodic recoating of the oxidized surface

Authors
Journal
Optics Communications
0030-4018
Publisher
Elsevier
Publication Date
Volume
135
Identifiers
DOI: 10.1016/s0030-4018(96)00632-3
Keywords
  • Condensed Matter
Disciplines
  • Physics

Abstract

Abstract In-orbit operating optical instruments provided with pure aluminum coatings are expected to promote great advances in far ultraviolet (FUV) astronomy. A difficulty to be overcome however, is the oxidizability of aluminum coatings in low earth orbits (LEO), where the residual atmosphere is constituted mainly by atomic oxygen. It is here demonstrated that the lifetime of an aluminum coating oxidized by limited exposures to atomic oxygen can be substantially extended by periodic recoating of the oxidized aluminum surface with new aluminum coatings. Recoating thicknesses of 30 and 60 nm are shown to completely recover the near normal FUV reflectance in the case of a mirror exposed to doses of atomic oxygen which caused decreases in the reflectance of about 13% and 30%, respectively, at 104.8 nm. After ten recoatings the reflectance of the primary aluminum film was completely recovered. Accordingly the lifetime of an aluminum coating placed in a LEO could be increased by an order of magnitude or more.

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