Solar ultraviolet-B detectors using Eu2+ doped alkali halide crystals

The continuous depletion of the ozone layer causes an increase in the ultra violet-B (UV-B) reaching the Earth's surface. In this paper the behaviour o f the KCl:Eu2+ under solar UV irradiation has been investigated. Considerin g the thermoluminescence (TL) excitation spectra, the geometrical solar rad iation parameters (solar zenith angle related to the light path) and the at mosphere characteristics (ozone content, Rayleigh scattering and aerosols' concentration), the solar UV irradiation Aux registered by the dosimeter ha s been simulated throughout the day. This modelled hourly signal agrees wit h the measured TL signal at different hours. Moreover, these curves through out the day are compared to the convoluted signal obtained from a gaussian curve centred at different UV-C wavelengths and the same solar spectrum. Th is comparison supports the idea that the KCl:Eu2+ crystal behaves under the sun as a narrow band gaussian detector centred at about 265 nm, but with t he main registered solar UV-B signal at 285 nm. On the other hand, a compar ison of the KCl:Eu2+ system with commercially available broad band UV-B bio logical sensors (biometers), shows that the europium doped crystals are mor e sensitive to minor changes of the solar UV-B flux and therefore, it is a good instrument for the study of small ozone layer depletions. (C) 2001 Els evier Science B.V. All rights reserved.