AMS measurement of C-14 concentration in a single-year ring of a 2500-yr-old tree

摘要

The ~(14)C concentration in rings of an old tree that date back approximately 2500 yr has been measured at single-year intervals with a highly accurate liquid scintillation counter (LSC) (0.2%) to investigate the 11-yr periodicity of solar activity. To investigate the applicability of AMS to accurate ~(14)C measurement, 16 graphite samples produced from the cellulose of a single-year tree ring of a 2500-yr-old cedar were measured with the micro analysis laboratory tandem (MALT) accelerator, at The University of Tokyo, and the results were compared with the ~(14)C age determined using LSC. The average ~(14)C age of the single-year tree ring calculated from 16 measurements was 2496 +- 23 yr BP, corresponding to the statistical accuracy of 0.26%. This was consistent with the age of 2514 +- 23 yr BP determined using LSC within the acceptable error range, which indicates that accelerator mass spectrometry (AMS) is applicable for accurate ~(14)C measurement using multi-graphite for the same single-year tree ring.