Accelerator Mass Spectrometry and Its Application to High-Precision Radiocarbon Dating

Abstract

Accelerator mass spectrometry (AMS) has developed wide application of radiocarbon (¹⁴C) dating. The AMS system requires only 1 mg of carbon in precise determination of ¹⁴C/ ¹²C and ¹³C/ ¹²C isotope ratios, and this advantage has broadened the applicability of ¹⁴C measurements. Nowadays, AMS contributes to the researches that utilize ¹⁴C dating in archeology, cultural property science, geology, and those that employ ¹⁴C tracer in environmental sciences, medical sciences and even forensic studies.

A Tandetron AMS system dedicated to ¹⁴C measurement was installed at Nagoya University, and its routine operation for ¹⁴C measurement was started in 1983 for the first time in Japan. In 1996, another AMS system (HVE-Model-4130-AMS) was purchased and has been used for high precision ¹⁴C measurements. By repeating a 30 minutes measurement of carbon isotopes for consecutive three days for a sample, one-sigma uncertainty of ±17 to ±30 years has been achieved. A reproducibility test for 2000-year-old archeological samples yielded a fluctuation error as small as ±11 years. We also have evaluated accuracy in our ¹⁴C measurements by participating in international ¹⁴C inter-comparison tests, and confirmed that our ¹⁴C results were quite consistent with those evaluated by the majority of participants. After the critical tests, we are sure that our AMS system is applicable to historical samples that require high precision as well as high accuracy ¹⁴C measurements.