In Situ Optical Characterization of Bulk Optical Glasses Under Protons and X-Rays.

We performed TRIUMF in situ measurements of the levels and kinetics of radiation-induced attenuation (RIA) caused by protons in different bulk optical glasses. Two SCHOTT radiation-hardened glasses (doped with Cerium) and six standard optical glasses (without Cerium) have been characterized. We compared the proton RIA kinetics with those resulting from in situ X-ray irradiations performed at dose and dose rate equivalent to the proton testing ones. The RIA spectra and kinetics are quite comparable in both cases, showing that X-rays can efficiently be used to estimate the RIA caused by protons. To better discuss the differences, we performed Monte Carlo calculations with GEANT4 of the energy deposition coefficient for each glass, according to its composition, and for the different beams. We complete our experimental characterization by comparing our data with those measured by the European Space Agency on the same glasses after $\gamma $ -irradiation. Protons, X-rays and $\gamma $ -rays cause RIA with very close spectral dependences, producing the same defects at similar concentration levels. We also demonstrated that the optimized setup for the in situ RIA characterization of bulk materials is very suitable for measurements under collimated particles beam. [ABSTRACT FROM AUTHOR]