Paramagnetic centers in glasses and glass-ceramics induced by simulated space radiation

Abstract

The electron paramagnetic resonance spectra of optical borosilicate glass, optical lead silicate glass, and a glass-ceramic were measured in order to predict their performance in space and to identify typical radiation damages in these commercially available materials. Space radiation in low earth orbits was simulated by 0.05 to 1.35 MeV electrons, 20 MeV protons from accelerators and tungsten tube X-rays with doses ranging from 10 2 to 10 8 Gy. EPR spectra recorded at room temperature after irradiation showed that the degree of damage depends on dose, but the types of point defect do not depend on dose. Within the investigated dose ranges the EPR absorptions measurable at room temperature were similar for the three radiation types, depending on the glass composition only, but not on radiation type and dose. The following material-specific defects were identified: oxygen hole centers (OHCs) and Fe 3+ in borosilicate glass and Zerodur, the electronic centers Zn +, Ti 3+ and Zr 3+ in Zerodur and a valence change in lead silicate glass: Pb 4++Fe 2+→Pb 3++ Fe 3+. OHC and Fe 3+ signals appear after 10 3 Gy, before macroscopic changes in transmission losses are detectable.