Supralinearity and sensitivity changes in optically stimulated luminescence of annealed quartz

The supralinear behaviour of the optically stimulated luminescence (OSL) signal is examined in an annealed quartz sample. Such investigations are important in luminescence dating and retrospective dosimetry, especially when the supralinearity intercept comprises a significant component of the paleodose in the sample. The sensitivity-uncorrected OSL growth curve of the annealed quartz sample 3-1/1 is observed to be supralinear in the dose range 0-5 Gy; it is then linear until about 20 Gy; and becomes sublinear beyond 20 Gy. The low-dose supralinearity is completely removed after a correction for sensitivity change. It is shown that the competing trap model (Kristianpoller, N., Chen, R., Israeli, M., 1974. Dose dependence of thermoluminescence peaks. Journal of Physics D: Applied Physics, 7, 1063-1072) and the competing centre model (McKeever, S.W.S., Chen, R., 1997. Luminescence models. Radiation Measurements, 27, 625-661) originally proposed to explain the supralinearity in thermoluminescence of quartz, can also be applied to explain supralinearity in the OSL response of the annealed quartz sample. Furthermore, cycle-dependent sensitivity changes are observed in another annealed quartz sample (NLT-28199) during repeated regeneration cycles. The OSL sensitivity decreases with cycle in this sample; this decrease is explained in terms of a recent model proposed by McKeever et al. (McKeever, S.W.S., Agersnap Larsen, N., Botter-Jensen, L., Mejdahl, V., 1997. OSL sensitivity changes during single aliquot procedures: computer simulations. Radiation Measurements 27, 75-82). (C) 2001 Elsevier Science Ltd. All rights reserved.