Estimation of Ultraviolet Radiation Dose Using CaF2:Tb Phosphor

Abstract

To observe and estimate the dose of ultraviolet (UV) radiation in sunlight, the available thermoluminescence (TL) materials were studied. Several kinds of lanthanide elements were doped in pure CaF2 powdered crystals and the properties of the TL for UV were observed. The TL intensity from CaF2Tb was the highest among the samples doped with various lanthanide elements, and from the TL emission spectra (380-540 nm) the TL is estimated to be due to inner transition of Tb3+. The peak wavelength of the TL excitation light was located approximately at 235 nm and light of a longer wavelength than 320 nm was unable to excite the TL. The ultraviolet response of CaF2:Tb depended on its sintering temperature. Even without ? ray pre-irradiation the CaF2:Tb sample with 1 h exposure to sunlight has enough sensitivity to estimate the change of UV. Seasonal change of UV intensity in sunlight was measured with this TLD during four months in 1993. The results agreed with that of other institutes in Japan.