An integrating ultraviolet-B dosemeter using phototransferred thermoluminescence from alpha-Al2O3:C

Until recently, atmospheric ozone has reflected all but approximately 1% of wavelengths below 320 nm. Recent evidence of ozone depletion in the stratosphere has generated interest in the biological impact on plants and animals resulting from increased exposure to these wavelengths. This has created a need for ultraviolet dosimetry of wavelengths shorter than 320 nm, particularly at southern latitudes. This paper describes the design of a dosemeter which measures absorbed ultraviolet dose, for the wavelength band centred at 307 nm, based upon the phototransferred thermoluminescence properties of alpha-Al2O3:C. Thin-layer alpha-Al2O3:C detectors were used. The calibrated response of the detectors has an average standard deviation of 2.7%. This dosemeter can be used in air or in water. The dosemeter has a near-linear ultraviolet dose response with a dynamic range of at least 3 decades (from an energy fluence of 10(2) mu J.cm(-2) to 10(5) mu J.cm(-2)) and very little temperature dependence in the region of biological interest (273-323 K). The inherent angular dependence of the interference tilter used in the dosemeter is partially flattened due to the wavelength dependence of the phototransferred thermoluminescence efficiency in this wavelength region, the shift in the transmission wavelength of the filter as a function of incident angle and through the use of diffusers.