Radiocarbon analysis on the new 1 MV multi-element BNUAMS system

Abstract BNUAMS is a newly commissioned, fully configured 1 MV accelerator mass spectrometry (AMS) system designed for multi-element trace isotope ratio measurements. The system was established in 2024 at the State Key Laboratory of Earth Surface Processes and Disaster Risk Reduction, Beijing Normal University, China. BNUAMS system demonstrates high sensitivity for trace radioisotopes measured by AMS, covering nuclides from beryllium-10 to plutonium-240. After six months of commissioning, routine measurements of 10 Be, 14 C, 26 Al, 41 Ca, 129 I, 239,240 Pu, and 236 U were successfully established. For radiocarbon determination, a precision better than 0.3% (1σ) in the 14 C/ 12 C ratio was achieved for OX-II standards. Background levels exceeding 50 kyr BP were obtained from processed dead wood and calcite samples. Commercial graphite and phthalic anhydride were measured to assessed the machine background (∼60 kyr BP) and processed background (∼50 kyr BP) respectively. Furthermore, measurements of IAEA-C5 and FIRI-D secondary reference materials agreed with consensus values within the 2σ uncertainty range.