Characterization of natural CaF2 crystals for radiation detection purposes

In this study, co-located natural fluorite crystals of varying colours were comprehensively investigated to elucidate their defect structures using spectroscopic techniques. Detailed analyses revealed oxygen ion-vacancy defect complexes in yellow fluorites and F-centers alongside self-irradiation-induced metallic calcium in purple fluorites. The thermoluminescence (TL) glow curve of natural CaF2 becomes saturated due to the high natural dose. Therefore, all TL studies were conducted after resetting the signal at an optimized annealing temperature of 400 °C. Raman spectroscopy identified 400 °C as the optimal annealing temperature, aligning the defect structures of natural CaF2 with those of synthetic fluorites. TL measurements demonstrated a linear beta dose response of the net TL output ranging from 3 to 7000 mSv (Adj. R2 = 0.99), meeting a key criterion for dosimetry. The findings underscore the significant potential of natural CaF2 crystals as reliable dosimetric materials for radiation monitoring.