Retrospective dosimetry: estimation of the dose to quartz using the single-aliquot regenerative-dose protocol.

We report on the application of the single-aliquot regenerative-dose protocol to retrospective dosimetry, using the optically stimulated luminescence (OSL) from quartz extracted from fired bricks. These bricks had previously been exposed to enhanced levels of ionising radiation while part of inhabited structures in the Chernobyl area. The time dependence of the OSL signals is considered first and we conclude that it is most appropriate to use the initial part of the OSL signal for dose estimation, after subtraction of a slowly varying background component. It is then shown that this signal meets the fundamental requirement of the single-aliquot regenerative-dose protocol, in that any change in the luminescence recombination probability can be corrected for by using the OSL response to a fixed test dose. The response of a particular aliquot is examined after three different treatments (untreated, reset by exposure to light and reset by heating to 500 degrees C) and it is shown that, after sensitivity correction, the dose-response curves are indistinguishable up to 10 Gy. The routine application of the protocol is then described and dose estimates are shown to be insensitive to preheat temperature and test-dose size. Finally, dose-depth profiles are presented for two bricks. These profiles demonstrate that the high precisions (approximately 1%) obtained using the regenerative-dose protocol are reflected in smooth dose-depth dependencies.