Available online at www.sciencedirect.com Radiation Measurements 37 (2003) 305–313 www.elsevier.com/locate/radmeas Environmental dose rate heterogeneity of beta radiation and its implications for luminescence dating: Monte Carlo modelling and experimental validation R.P. Nathan a ; ∗ , P.J. Thomas b; c ,M.Jain d , A.S. Murray b , E.J. Rhodes a a Research Laboratory for Archaeology and the History of Art, University of Oxford, 6 Keble Road, Oxford, OX1 3QJ, UK b The Nordic Laboratory for Luminescence Dating, Department of Earth Sciences, Aarhus University, Ris National Laboratory, Roskilde, DK-4000, Denmark c Department of Quaternary Geology, Lund University, Lund, SE-22363, Sweden d Ris National Laboratory, Roskilde, DK-4000, Denmark Abstract The recent development of rapid single sand-sized grain analyses in luminescence dating has necessitated the accurate interpretation of De distributions to recover a representative De acquired since the last bleaching event. Beta heterogeneity may adversely aect the variance and symmetry of De distributions and it is important to characterise this eect, both to ensure that dose distributions are not misinterpreted, and that an accurate beta dose rate is employed in dating calculations. In this study, we make a rst attempt providing a description of potential problems in heterogeneous environments and identify the likely size of these eects on De distributions. The study employs the MCNP 4C Monte Carlo electron/photon transport model, supported by an experimental validation of the code in several case studies. We nd good agreement between the experimental measurements and the Monte Carlo simulations. It is concluded that the eect of beta heterogeneity in complex environments for luminescence dating is two fold: (i) the innite matrix dose rate is not universally applicable; its accuracy depends on the scale of the heterogeneity, and (ii) the interpretation of De distributions is complex and techniques which reject part of the De distribution may lead to inaccurate dates in some circumstances. c  2003 Elsevier Science Ltd. All rights reserved. Keywords: Radiation heterogeneity; Luminescence dating; Beta dose 1. Introduction 1.1. Background Luminescence dating requires solution of Eq. (1) t = De ˙ D ; (1) where t is the duration since deposition, De is the equiv- alent absorbed dose measured in the laboratory, and ˙ D is the dose absorbed per unit time. Major advances in optically stimulated luminescence (OSL) equivalent dose * Corresponding author. Tel: ++44-1865-283033; fax: ++44- 1865-273932. E-mail address: roger.nathan@rlaha.ox.ac.uk (R.P. Nathan). determinations, both in terms of procedural innovation such as the single-aliquot regenerative-dose protocol (SAR) (Murray and Wintle, 2000) and instrumentation such as the automated RisH reader with single grain facilities (BHtter-Jensen and Murray, 2002), have served to increase the reliability and quantity of information available from a sample. The measurement of De distributions using small aliquots or single grains is becoming routine. The interpre- tation of De distributions to nd a representative De for the bleaching event of interest, however, remains a very active research area in luminescence dating, primarily due to a number of potential sources of variance and asymmetry that may exist (Murray and Roberts, 1997). Several approaches have been suggested for De interpretation based on the expected eects of well-known problems, such as incom- plete bleaching or grain migration (e.g. Lepper et al., 2000; 1350-4487/03/$-see front matter c  2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S1350-4487(03)00008-8