Present status of the YU-AMS system and its operation over the past 10 years
Dr Mirei Takeyama1, Mr Toru Moriya1, Dr Hisako Saitoh2, Dr Hiroko Miyahara3, Dr Motonari Ohyama4, Dr Hirohisa Sakurai5, Dr Fuyuki Tokanai1,5
1Center for Accelerator Mass Spectrometry, Yamagata University, Kaminoyama, Japan, 2Department of Legal Medicine, Graduate School of Medicine, Chiba University, Chiba, Japan, 3Humanities and Sciences / Museum Careers, Musashino Art University, Kodaira, Japan, 4Botanical Gardens, Tohoku University, Sendai, Japan, 5Faculty of Science, Yamagata University, Yamagata, Japan
In 2009, Yamagata University (YU) installed a compact ¹⁴C accelerator mass spectrometry (YU-AMS) system and an automated graphitization line (AGL I) in Yamagata Research Institute located in Kaminoyama City. The AMS system is based on a 0.5 MV Pelletron accelerator (CAMS) developed by National Electrostatics Corporation. This AMS system was the first AMS system installed in a university in northern Japan (Tohoku–Hokkaido region). In March 2014, a second automated graphitization line (AGL II) and a second ion source on the AMS system were installed. AGL II consists of an elemental analyzer (EA, Vario MICRO cube, Elementar) and a glass vacuum line. It has the same graphitization process as the previously installed AGL I except for the procedure of stable isotope ratio mass spectrometer (IRMS) measurement. The AGL works as follows. A sample whose ¹⁴C content is to be measured is packed in a tin capsule. The packed sample is then set in the autosampler in EA, where it is automatically combusted at 1150 °C. In this process, N₂, O₂, and CO₂ are generated. The CO₂ gas is transferred to a cryogenic CO₂-trapping system, consisting of 20 identical glass lines. The trapped CO₂ is finally reduced to graphite at 630 °C using hydrogen and an iron powder catalyst. The collection of CO₂ and the addition of H₂ used for CO₂ reduction are automatically conducted. An additional ion source can be used for subsequent measurement by setting samples in a chamber and evacuating the chamber while the other source is being used for AMS measurement. Hence, this system can shorten the total measurement time.
Approximately 2,000 samples are measured per year using the system. The facility is capable of treating more than 3,000 samples per year. The samples most commonly measured using the YU-AMS system over the last 10 years (2010–2020) were wood (~70%). The second and third most commonly measured samples were charcoal and soil, respectively, which were mainly extracted from historical remains. The long-term stability of the YU-AMS system has been routinely assessed by measuring the IAEA-C7 standard sample. The average ¹⁴C activity for IAEA-C7 measured using the system is 49.52 ± 0.11 pMC (percent modern carbon), which is in good agreement with the consensus value of 49.53 ± 0.12 pMC. Using the YU-AMS system, we have been carrying out studies in various fields such as archaeology, environmental science, geology, and space and earth sciences. Recently, we have also been expanding our research into the field of forensic medicine. In this conference, we will report on the present status of the YU-AMS system and its operation over the past 10 years.
PhD (Science) at Yamagata University, Master of Science at Yamagata University, Bachelor of Science at Yamagata University
Currently Technical Specialist – Center for Accelerator Mass Spectrometry, Yamagata University
Roles: Sample preparation and advanced research, Technological development for isotope measurement and equipment performance enhancement, Development and research of radiation measuring instruments
Previously, Technical Staff (2015-2021), Center for Accelerator Mass Spectrometry, Yamagata University and Junior Research Associate (2013-2015), Nishina Center for Accelerator-Based Science, RIKEN.