Proton-induced changes of optical properties and defect formation in quartz glasses

Optical absorption and luminescence of three quartz glass types (KI, KV, KU-1) with different impurities exposed to proton fluences of 10(13)-10(16) protons/cm(2) were studied. The role of ionisation and elastic energy losses resulting in defect formations along the proton track was considered. On a larger part of the track, for proton energies E-p greater than or equal to 5 MeV, defect creation is due to ionisation energy losses and the colour and luminescence centers are mainly formed by means of recharge of native defects. As a result on this part of the track the numbers of the [=Si-O Al=] and E'-centers grow as the proton fluence increases. For proton energies to E-p < 5 MeV the creation of structural defects, like displaced atoms and their vacancies, dominates by means of elastic atom collisions with protons and recoil atoms. This leads to intensive generation of E'-centers and to a more rapid increase of absorption at 215 nm in all glasses and to a destruction of the alumina-alkaline centers in KI glasses. At the end of the proton track the transformation of [=Si-], [=Si-O-] and [=Si-O-Al=] centers into [=Si-H], [=Si-OH] and [=Si-OH Al=] centers is probable, because the free bonds can be occupied by the stopping protons.