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Measurement of low (super 14) C activities in a liquid scintillation counter in the Zagreb Radiocarbon Laboratory.

Nada Horvatincic, Jadranka Baresic, Ines Krajcar Bronic, Bogomil Obelic

Abstract


Two methods of chemical preparation of radiocarbon samples are implemented in the Zagreb Radiocarbon Laboratory for measurement by a new liquid scintillation counter (LSC), Quantulus 1220 (super TM) : a CO (sub 2) absorption method (LSC-A) and a benzene synthesis method (LSC-B). For samples prepared by both methods, the optimal counting windows for measurement in LSC were determined. The total efficiency of LSC-A is 65% and that of the LSC-B is 83%, while the corresponding (super 14) C dating limits are 31,800 yr and 52, 160 yr, respectively. (super 14) C activities measured by the LSC-A and LSC-B methods were compared with those measured by the gas proportional counter (GPC) method (efficiency 75%, (super 14) C dating limit 37,500 yr). The results obtained by the LSC-A method have larger errors than those measured by the GPC method, but LSC-A is quick, inexpensive, simple, and requires less carbon than the GPC method. Thus, LSC-A is suitable for (super 14) C measurements of geological, hydrological, and environmental samples. On the other hand, the results obtained by the LSC-B method give smaller errors and a larger (super 14) C dating range. Therefore, LSC-B is more suitable for (super 14) C dating of archaeological samples.

Keywords


absolute age;absorption method;archaeology ;benzene synthesis method;C 14;carbon ;carbon dioxide;Croatia ;errors ;Europe ;instruments ;isotopes ;liquid scintillation methods;measurement ;methods ;radioactive isotopes;Southern Europe;Zagreb Croatia;Zagreb Radiocarbon Laboratory

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