Investigations on radiation-induced processes in dielectric materials

Features of experimental study and changes of electrical properties of dielectric materials under irradiation are reviewed. The results on radiation-induced conductivity (RIC) in single crystal Al2O3 exposed to fast reactor neutrons up to the dose of 4.7 x 1024 n/m2 and in single crystal Al2O3 and pyrolitic BN exposed to 7 MeV proton irradiation up to a dose of 2 x 1020 p/m2 are presented. In both cases, RIC did not exceed 10-12 S/cm, the initial value of the conductivity being equal to 10-14 S/cm. Results of calculations and measurements of likely leakage currents are presented. Formation of carbon and hydrocarbon layers on the surface results in the apparent phenomenon of radiation-induced electrical degradation of dielectrics. The defect clustering in dielectrics occurs in cascades and tracks during the thermal spikes. Under the doses of 3.3-3.5 x 1025 n/m2 dielectric breakdown strength of Al2O3 is two times as small, and the mechanical strength is 35.5% higher than initial values. The radiation-induced electrical degradation in metal-dielectric systems can be significant. (orig.)