The wavelength dependence of light-induced fading of thermoluminescence from α-Al 2O 3:C

Abstract

This paper reports on the wavelength dependence, over the range 340–650 nm, of the light-induced fading of the main dosimetric TL signal from α-Al 2O 3:C. The data were obtained for either fixed photon flux or fixed photon energy, using either samples which were annealed after each TL readout and before re-use or samples which were unannealed. Photoconductivity and PTTL data suggest that the fading is due to the optical stimulation of charge from the traps into the delocalized bands. At a given wavelength the decay is approximately first-order for the first 90% of the decay. The decay constant, for a given photon flux, is dependent upon wavelength in the same manner as the efficiency for TL fading. At short wavelengths it is necessary to accout for the phototransfer of charge from deep traps into the dosimetry traps and thus the exact wavelength dependence is governed by the radiation and thermal history of the sample. The dose dependence of the TL peak suggests that it is caused by an overlap of several peaks resulting from an array of closely spaced energy levels.