PARAMAGNETIC CENTERS IN GLASSES AND GLASS-CERAMICS INDUCED BY SIMULATED SPACE RADIATION

The electron paramagnetic resonance spectra of optical borosilicate gl ass, optical lead silicate glass, and a glass-ceramic were measured in order to predict their performance in space and to identify typical r adiation damages in these commercially available materials. Space radi ation 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 temperatu re after irradiation showed that the degree of damage depends on dose, but the types of point defect do not depend on dose. Within the inves tigated dose ranges the EPR absorptions measurable at room temperature were similar for the three radiation types, depending on the glass co mposition only, but not on radiation type and dose. The following mate rial-specific defects were identified: oxygen hole centers (OHCs) and Fe3+ in borosilicate glass and Zerodur, the electronic centers Zn+, Ti 3+ and Zr3+ in Zerodur and a valence change in lead silicate glass: Pb 4+ + Fe2+ --> Pb3+ + Fe3+. OHC and Fe3+ signals appear after 10(3) Gy, before macroscopic changes in transmission losses are detectable.