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Tallinn Radiocarbon Dates VII

Published online by Cambridge University Press:  18 July 2016

J M Punning
Affiliation:
Institute of Geology, Academy of Sciences, Tallinn, ESSR
R Rajamäe
Affiliation:
Institute of Geology, Academy of Sciences, Tallinn, ESSR
Kai Joers
Affiliation:
Institute of Geology, Academy of Sciences, Tallinn, ESSR
H Putnik
Affiliation:
Institute of Geology, Academy of Sciences, Tallinn, ESSR
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This list comprises age measurements carried out at the Institute from 1979 to 1981. Anticoincidence variant was applied to attain higher counting efficiency of a 2-channel scintillation device. The introduction of a plastic scintillator as an active guard around the detector in the 2π geometry decreases the influence of high energy cosmic radiation and reduces the background ca 35 to 75% (Rajamäe & Punning, 1980). The application of an active guard with 4π geometry has proved most effective; as a result, the background decreased 85% to 0.65cpm with the volume of scintillation cocktail 5ml. We have improved our methods for decreasing the actual error of the background. The application of a control channel and consideration of barometric effect results in the increase of dating limits of up to 5000–6000 years (Rajamäe, 1981). Samples are calculated using a half-life of 5568 ± 30 years for 14C. Results are reported in years before 1950. δ13C measurements were performed on the mass-spectrometer MI-1201 and are reported with PDB as a reference standard. The reproducibility of results is ±0.2‰.

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