Optical and electrical phenomena in dielectric materials under irradiation

Optical and acoustic properties of the materials based on Al2O3, SiO2 and BN under 8 MeV proton irradiation (<10(4) Gy/s) have been measured. Electric charge partitioning has been shown to result in charging the microscopic regions in the bulk of the dielectrics under irradiation, which is due to different mobility of free electrons and holes (sapphire), concentration inhomogeneity in the system of charge carrier traps (alumina), or thermodynamic instability of the homogeneous distribution of the filled traps (silica glasses). Prevalent charge carrier recombination in the grain boundaries causes re-crystallization of pyrolitic boron nitride under irradiation, which shows up as simultaneous decrease of the intensity of radiation-induced luminescence (RIL) of the centres in the grain boundaries and the BN. The local charging results in optical inhomogeneity of the silica glasses which is sustained by the optical loss spectra of the irradiated glasses, features of kinetics of bleaching, RIL kinetics and dose dependence of the ultrasonic vibration decrement. (C) 2002 Elsevier Science B.V. All rights reserved.