Characteristic of Substrate Coloration Under Space Charged Particles

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Characteristic of Substrate Coloration Under Space Charged Particles

Liu, Hai / Zhao, Huicong

Abstract The radiation induced transmittance change of the lens with antireflection films of MgF2/ZrO2/Al2O3 on both surfaces was investigated under the 60–1000 keV electron and/or proton radiation on a space complex radiation simulator. The results show that the transmittance of lens is monotonously decreased with increasing radiation fluence. The major absorption band around 430 nm is caused by F2 center, F+ center and VŌH center in the antireflection films. The weak absorption band in 500–800 nm is related to the hole-type color center and the impurity-type color center under higher radiation fluence. Under the proton energy <100 keV, the radiation induced damage of antireflection films dominates the variation of transmittance, which is increased with increasing radiation energy. When the energy exceeds 100 keV, the energy loss in films is reduced and the substrate coloring becomes the main cause for the transmittance change. Under electron radiation, the change of transmittance increases with increasing energy while the energy loss in films dramatically decreases with increasing electron energy. In this case, the radiation induced effect on substrate is a dominant factor. The coloration of films also has certain contribution to transmittance change due to the scattering effect of electrons. In the near-Earth space, electron fluxes are higher than proton ones and the fluxes of low-energy charged particles are higher than high-energy charged particles. Therefore, for evaluation of radiation effects on the optical elements with films, the low-energy electron exposures are preferred, with the low-energy proton exposures being the second option.