Threshold for displacement defect production in electron-irradiated alumina

Ceramic materials are being investigated as potential insulators in fusion reactors because of their ability to withstand the high temperatures of operation and high radiation levels. The threshold energy for atomic displacement, 0.30 MeV, is considerably lower than the value of approx 0.40 MeV previously measured. At 0.30 MeV, an electron will transfer a maximum energy of 53 eV to the oxygen atom. Crystals of alpha -Al sub 2 O sub 3 were irradiated by an electron accelerator. The luminescence emission from the samples was focused onto the entrance slit of a monochromator whose output was monitored by a photomultiplier and displayed on a fast storage oscilloscope. Emission intensity--time data were digitized from the oscilloscope using a video camera and an LSI-11 computer system.