Abstract
Terrestrial accelerator facilities can generate ion beams which enable the testing of the resistance of materials and thin film coatings to be used in the space environment. In this work, a hbox {TiO}_2/Al bi-layer coating has been irradiated with a hbox {He}^+ beam at three different energies. The same flux and dose have been used in order to investigate the damage dependence on the energy. The energies were selected to be in the range 4–100 keV, in order to consider those associated to the quiet solar wind and to the particles present in the near-Earth space environment. The optical, morphological and structural modifications have been investigated by using various techniques. Surprisingly, the most damaged sample is the one irradiated at the intermediate energy, which, on the other hand, corresponds to the case in which the interface between the two layers is more stressed. Results demonstrate that ion energies for irradiation tests must be carefully selected to properly qualify space components.
Highlights
Terrestrial accelerator facilities can generate ion beams which enable the testing of the resistance of materials and thin film coatings to be used in the space environment
The degradation is dramatic because the reflectance is predominantly determined by the degradation of the interface between the TiO2 capping-layer and the first few tens of nm of the Al layer; starting from the extinction coefficient k, the penetration depth γp estimated for aluminum is < 7.5 nm in the visible spectral range, so that all the changes in the Al layer occurring deeper than ≃ 2γp = 15 nm do not significantly affect the reflectance performance
In the case of the reference sample, a value of 3.2 nm was estimated, which is compatible with the Atomic Force Microscope (AFM) measurements reported in “Morphological analysis” section
Summary
Terrestrial accelerator facilities can generate ion beams which enable the testing of the resistance of materials and thin film coatings to be used in the space environment. The energies were selected to be in the range 4–100 keV, in order to consider those associated to the quiet solar wind and to the particles present in the near-Earth space environment. With the advent of new space missions operating in hostile environments, such as those in low-perihelion solar orbits and those studying the Jovian magnetosphere, the need to understand the effects of the irradiation of charged particles such as electrons, protons, and He ions has e merged[1]. MeV protons and electrons are abundant, for example in low-earth-orbit, as they are trapped in the Van Allen b elts[3] Due to their limited thickness (between few and hundreds of nanometers), thin film coatings are mostly affected by keV ions, as these implant within the material, changing their optical and structural properties. Low-energy particles have been demonstrated to be present in planetary atmospheres, including terrestrial o rbits[5]
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