Thermoluminescence of electron-irradiated CaF2

Abstract

Storage of excitation energy in CaF2 crystals, irradiated by low- energy electrons, is found to be very much less compared to x-ray irradiation; the TL (thermoluminescence) yield is, in general, very poor for all the temperatures of excitation between 300 and 500 deg K. While the crystal, excited by electrons at RT, shows a complex distribution of glow maxima in the temperature region between 300 and 700 deg K, it does not seem to show any TL for excitation at about 500 deg K or above; in the latter case the crystal becomes densely colored and shows alpha and BETA absorption bands. The comparatively low intense glow peaks occurring below 500 deg K may be associated with the trapping states related with the trace impurities. Absence of TL in the colored crystal is explained by assuming that, during the process of excitation at or above 450 deg K trapped holes diffuse away from the affected layer and facilitate the formation of alpha and BETA absorption bands.