Status report on Laboratory of Radiocarbon Dating, The University Museum, The University of Tokyo, Japan

Dr Takayuki Omori1, Dr Hiromasa Ozaki1, Mr Kohei Yamazaki1, Mr Ayao Kanesawa1, Ms Fumina Minamitani2, Prof Minoru Yoneda1,2

1The University Museum, The University of Tokyo, 7-3-1, Hongo, Bunkyo, Japan, 2Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwa, Japan

0.5 MV compact Accelerator Mass Spectrometry (CAMS) system (1.5SDH-1, NEC), customized for museum exhibitions, was installed in the Laboratory of Radiocarbon dating at the University Museum, the University of Tokyo (LRD.UMUT) in 2014. The CAMS in the exhibition space has welcomed more than one hundred thousand visitors and supported chronological research and academic projects. More than five years after the laboratory was renewed as an AMS facility, the 14C data accumulation and facility improvements proceeded. This paper provides current laboratory status and measurement performance.
As a small group, LRD.UMUT achieved more than ten thousand measurements with optimized sample preparations and stable AMS operations. Primary applications focus on archaeology, anthropology, and earth sciences that handle various types of materials. The chemical laboratory is ready for comprehensive approaches, from conventional pretreatments to improved chemical treatments, such as ABOx-Stepped combustion, Carbonate Density Separation (CarDS), and Ultrafiltration, including sample screenings using FT-IR, XRD, and EA. The preparation of an AMS target is available from the standard 1 mgC to less than 100 μgC, for small samples operating in an original remote and automation EA-based system. The efficiency of the target preparation is two thousand samples/person in a year, and the data stability increased more than manual preparations.
The AMS system, comprised a solid-state ion source (MC-SNICS) and a 0.5 MV accelerator, maintains a measurement error of less than ±0.3%, keeping a low background around 0.1 pMC. The stable measurements are due to the power supply and temperature control for each component, resulting in success with little changes in conditions, even after a long time of measurement (several days).
We summarize here the general procedures for 14C dating on LRD.UMUT, as well as quantitative comparisons regarding the schemes for the optimization and stability measurements.


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Date

Nov 08 - 19 2021