TY - JOUR
T1 - Simulations of thermally transferred OSL signals in quartz
T2 - Accuracy and precision of the protocols for equivalent dose evaluation
AU - Pagonis, Vasilis
AU - Adamiec, Grzegorz
AU - Athanassas, C.
AU - Chen, Reuven
AU - Baker, Atlee
AU - Larsen, Meredith
AU - Thompson, Zachary
PY - 2011/6/15
Y1 - 2011/6/15
N2 - Thermally-transferred optically stimulated luminescence (TT-OSL) signals in sedimentary quartz have been the subject of several recent studies, due to the potential shown by these signals to increase the range of luminescence dating by an order of magnitude. Based on these signals, a single aliquot protocol termed the ReSAR protocol has been developed and tested experimentally. This paper presents extensive numerical simulations of this ReSAR protocol. The purpose of the simulations is to investigate several aspects of the ReSAR protocol which are believed to cause difficulties during application of the protocol. Furthermore, several modified versions of the ReSAR protocol are simulated, and their relative accuracy and precision are compared. The simulations are carried out using a recently published kinetic model for quartz, consisting of 11 energy levels. One hundred random variants of the natural samples were generated by keeping the transition probabilities between energy levels fixed, while allowing simultaneous random variations of the concentrations of the 11 energy levels. The relative intrinsic accuracy and precision of the protocols are simulated by calculating the equivalent dose (ED) within the model, for a given natural burial dose of the sample. The complete sequence of steps undertaken in several versions of the dating protocols is simulated. The relative intrinsic precision of these techniques is estimated by fitting Gaussian probability functions to the resulting simulated distribution of ED values. New simulations are presented for commonly used OSL sensitivity tests, consisting of successive cycles of sample irradiation with the same dose, followed by measurements of the sensitivity corrected L/T signals. We investigate several experimental factors which may be affecting both the intrinsic precision and intrinsic accuracy of the ReSAR protocol. The results of the simulation show that the four different published versions of the ReSAR protocol can reproduce accurately the natural doses in the range 0-400 Gy with approximately the same intrinsic precision and accuracy of ∼1-5%. However, these protocols underestimate doses above 400 Gy; possible sources of this underestimation are investigated. Two possible explanations are suggested for the modeled underestimations, possible thermal instability of the TT-OSL traps, and the presence of thermally unstable medium OSL components in the model.
AB - Thermally-transferred optically stimulated luminescence (TT-OSL) signals in sedimentary quartz have been the subject of several recent studies, due to the potential shown by these signals to increase the range of luminescence dating by an order of magnitude. Based on these signals, a single aliquot protocol termed the ReSAR protocol has been developed and tested experimentally. This paper presents extensive numerical simulations of this ReSAR protocol. The purpose of the simulations is to investigate several aspects of the ReSAR protocol which are believed to cause difficulties during application of the protocol. Furthermore, several modified versions of the ReSAR protocol are simulated, and their relative accuracy and precision are compared. The simulations are carried out using a recently published kinetic model for quartz, consisting of 11 energy levels. One hundred random variants of the natural samples were generated by keeping the transition probabilities between energy levels fixed, while allowing simultaneous random variations of the concentrations of the 11 energy levels. The relative intrinsic accuracy and precision of the protocols are simulated by calculating the equivalent dose (ED) within the model, for a given natural burial dose of the sample. The complete sequence of steps undertaken in several versions of the dating protocols is simulated. The relative intrinsic precision of these techniques is estimated by fitting Gaussian probability functions to the resulting simulated distribution of ED values. New simulations are presented for commonly used OSL sensitivity tests, consisting of successive cycles of sample irradiation with the same dose, followed by measurements of the sensitivity corrected L/T signals. We investigate several experimental factors which may be affecting both the intrinsic precision and intrinsic accuracy of the ReSAR protocol. The results of the simulation show that the four different published versions of the ReSAR protocol can reproduce accurately the natural doses in the range 0-400 Gy with approximately the same intrinsic precision and accuracy of ∼1-5%. However, these protocols underestimate doses above 400 Gy; possible sources of this underestimation are investigated. Two possible explanations are suggested for the modeled underestimations, possible thermal instability of the TT-OSL traps, and the presence of thermally unstable medium OSL components in the model.
KW - Accident dosimetry
KW - Authenticity testing
KW - Equivalent dose estimation
KW - Kinetic rate equations
KW - Optically stimulated luminescence (OSL)
KW - Quartz
KW - Retrospective dosimetry
KW - SAR technique
KW - TT-OSL
KW - Thermoluminescence (TL)
UR - http://www.scopus.com/inward/record.url?scp=79955516887&partnerID=8YFLogxK
U2 - 10.1016/j.nimb.2011.03.026
DO - 10.1016/j.nimb.2011.03.026
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AN - SCOPUS:79955516887
SN - 0168-583X
VL - 269
SP - 1431
EP - 1443
JO - Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
JF - Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
IS - 12
ER -