To observe and estimate the dose of ultraviolet (UV) radiation in sunl
ight, the available thermoluminescence (TL) materials were studied. Se
veral kinds of lanthanide elements were doped in pure CaF2 powdered cr
ystals and the properties of the TL for UV were observed. The TL inten
sity from CaF2:Tb was the highest among the samples doped with various
lanthanide elements, and from the TL emission spectra (380-540 nm) th
e TL is estimated to be due to inner transition of Tb3+. The peak wave
length 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 temp
erature. Even without gamma ray preirradiation the CaF2:Tb sample with
1 h exposure to sunlight has enough sensitivity to estimate the chang
e 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.