Risø calibration quartz - A challenge for β-source calibration. An applied study with relevance for luminescence dating

Risø calibration quartz (RCQ) is used worldwide in luminescence laboratories to calibrate β-sources. RCQ is advantageous because the inherent γ-dose is determined conveniently with a blue light stimulated luminescence (BLSL) single aliquot regeneration (SAR) protocol and dose equivalents (DEs) are highly reproducible with standard errors of the mean of usually <2%. We report on a series of tests on the recoverability of known β-doses from RCQ and on DE-determination of γ-dosed RCQ with varying SAR-measurement parameters. Evaluated alone, these raise doubt whether the precise calibration results are systematically correct. However, it is likely that cutheat and preheat adjustment of 'quick calibration' as applied by staff members of the Radiation Research Division of the Technical University of Denmark when installing a new luminescence reader in a customer's laboratory are appropriate to minimize systematic errors. This finding is suggested by comparative calibration of a β-source with RCQ and another γ-irradiated quartz.