Discharge Figures in Dielectrics by Electron Irradiation

Abstract

The electrical breakage of glass shielding windows by intense gamma irradiation presents a severe problem for hot caves. To understand this phenomenon the authors studied the discharge conditions, their natures, and the decay of the accumulated electric charge by electron irradiation. The samples used were lead glass F62-R, nonbrowning lead glass F36-N, nonbrowning glass C-N, common window glass, polymethylmethacrylate (PMMA) and polyvinylchloride (PVC). Their specific gravities were 6.2, 3.6, 2.7, 2.5, 1.2, and 1.4 respectively. The samples were discharged by a steel needle pricking the surface prior to, or after, irradiation. The 2-MeV Van de Graaff generator and 15-MeV Linac were used in these experiments. The relation between irradiation doses and the largeness of discharge pattern in the samples and the decay of the discharge pattern after irradiation are described. The times in which the initial stored charge became its half-value were 30 min for PMMA, 70 h for PVC, 8 h for C-N and 90 h for F36-N.