Thermoluminescence and F-center annealing in alkaline-earth fluoride crystals after reactor irradiation at low temperature

Thermoluminescence is related to the F-center annealing stage in undoped alkaline-earth fluoride (CaF2, SrF2, and BaF2) single crystals irradiated at 20 K with reactor neutrons. The temperature of glow peak maxima are classified in four groups (P-1–4); P-1: 110–130 K, P-2: 134–152 K, P-3: 183–200 K and P-4: 201–245 K with a heating rate of 4 K/min. at temperatures ranging 77–300 K. These temperatures of peak maxima correspond well to decay stages of F-centers. F-centers play an important role as recombination centers in the TL process. The main TL emission spectrum of P-1–4 peaks consists of the intrinsic luminescence as well as the case of the x-ray emission spectrum at 77 K. It is revealed that these TL emission bands near 300 nm of P-1, 2, and 3 peaks are due to the radiative recombination of (VK+F) and (H+F) reactions, respectively.