A 14C AMS system built by HVEE, B.V., the Netherlands, was delivered to Nagoya University in 1996, finished final acceptance tests in January of 1999, and started routinely 14C measurements in 2000. The standard deviation (1sigma) of the 14C/12C ratios is around ±0.3% to ±0.4% (a bit larger than the uncertainty of about ±0.3% calculated from 14C counting statistics) and that of the corresponding 13C/12C ratios is ±0.03% to ±0.07%, as are tested for HOxII targets. The number of targets measured was 330, 1430, 2077, 1003 and 1679 in each year from 1999 to 2004, respectively. By using this AMS system, we are now trying to obtain high accuracy and high precision 14C data for tree ring samples for the test of the established INTCAL98 and INTCAL04 14C data sets whether they are consistent with the 14C-concentration records in Japanese trees.
Precise estimation of age for a historical event is getting more and more important in Japan. To provide accurate age to the event, an age estimation by 14C wiggle matching techniques for wood samples is quite promising. Therefore, we are conducting accuracy and precision tests by measuring 14C age for each annual ring of a big tree whose age was determined by dendrochronology. A wiggle matching to INTCAL04 of 14C ages measured for 55 annual rings of a big tree (a Japanese cedar) yielded a good agreement of its dendrochronological age to the best fit calendar year, with ±2 yr uncertainty (95 confidence level).
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