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A Simple, Extremely Stable Single-Tube Liquid Scintillation System for Radiocarbon Dating

Published online by Cambridge University Press:  18 July 2016

Pall Theodórsson
Pall Theodórsson*
Affiliation:
Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavík, Iceland. Email: [email protected]
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Abstract

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This paper describes a simple and compact liquid scintillation radiocarbon dating system, ICELS, and demonstrates its long-term stability and reproducibility to a precision level rarely presented before, better than 0.04% (3 14C yr). Inexpensive systems of this kind may, in the future, help to meet increasing demand for high precision (±16 to ±20 14C yr) and strict quality control. ICELS comprises a compact detector unit, where a 3-mL dome-shaped vial, with an optimal light reflector, sits on the top of a vertical 30-mm photomultiplier tube. Sample changing is manual. The high voltage is set at the balance point for each sample, securing maximal counting stability. The quench correction method used (spectrum restoration) corrects with 0.04% precision for all parameters that can normally shift the 14C spectrum. For 3 mL of benzene at 71% 14C counting efficiency (recent carbon 23 cpm), the background is 1.72 cpm behind a 5-cm-thick shield of lead (27 kg) and 1.53 cpm behind 10 cm of lead. The background count rate corrected for atmospheric pressure variations was completely stable over 47- and 57-d testing periods for the 2 systems.

Type
Articles
Information
Radiocarbon , Volume 47 , Issue 1 , 2005 , pp. 89 - 97
Copyright
Copyright © 2005 by the Arizona Board of Regents on behalf of the University of Arizona 

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