北京大学学报(自然科学版)

高精度加速器质谱14C测年

郭之虞   

  1. 北京大学重离子物理研究所,北京,100871
  • 收稿日期:1997-12-09 出版日期:1998-04-20 发布日期:1998-04-20

Radiocarbon Dating by Accelerator Mass Spectrometry with High Precision and Accuracy

GUO Zhiyu   

  1. Institute of Heavy Ion Physics, Peking University, Beijing, 100871
  • Received:1997-12-09 Online:1998-04-20 Published:1998-04-20

摘要: 加速器质谱14C测量误差的主要来源是14C计数的统计误差与束流传输的不稳定性。对高精度测量还要考虑束流积分仪中IFC的非线性及离子源中弹坑效应引起的时变分馏。为得到高精度的样品年代数据,除提高14C测量精度外,还要用系列样品进行高精度的树轮校正,并采取必要措施保证测量结果的可靠性。

关键词: 加速器质谱, 14C测年, 高精度

Abstract: The precision and accuracy of AMS 14C dating have been studied. The main source of error comes from the statistical error of 14C counting and the instability of beam transmission efficiency. For high precision measurement the non-linearity error of current-frequency- conversion in beam current integrator and the time-dependent fractionation introduced by crater effect in ion source should also be considered. To meet the requirement of Xia-Shang-Zhou Chronology Project, PKUAMS upgrade was carried out. The stability of power supplies and the system vacuum were improved. The ion source has been replaced by a new one with better performance and reliability. With new data acquisition system the precision of lived time readout could reach 0.005%-0.01%. In order to obtain high precision age data, it is necessary not only to improve the precision of 14C measurements, but also to use the series samples in dendrological calibration by wiggle-matching method based on the Bayesian approach. The reliability of sample age depends on suitable sample selection and preparation, as well as the elimination of systematic error in measurement.

Key words: accelerator mass spectrometry(AMS), 14C dating, high precision

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