Study on Experimental Conditions of Compact ¹⁴C Accelerator Mass Spectrometer

GXNU-AMS, a compact ¹⁴C accelerator mass spectrometer, jointly developed by the Chinese Institute of Atomic Energy and Guangxi Normal University, and it was installed and commissioned in Guangxi Normal University. Without the traditional mode of SF₆ pressure tank, the terminal of the system was designed as an open insulated high voltage platform, which reduces the construction size of the traditional accelerator to be about 2×2.5 square meters. Helium gas stripping was used to eliminate the interference of molecular ions, and the maximum operating voltage was 230 kV. At present, the measurement accuracy of the instrument is 0.5%, and the measurement sensitivity is ¹⁴C/¹²C≈1.0×10^-14 (measurement background is 40 000 years), which can meet the measurement requirements in the fields of life sciences and archaeology. In this paper, the experimental conditions and reliability of GXNU-AMS were studied. The pre-accelerator voltage and the main accelerator voltage were set to be 30 kV and 200 kV, respectively, the pressure of stripping gas was set to be 5.1×10^-3 Pa, and the charge state ⁺C was chosen after accelerated. The PMC value of the self-made standard sample was consistent with the values of international OXⅡ standard sample. The experiment results showed that the system can be operated with high measurement accuracy and good stability, which layed a good foundation for further research on this facility. This work is helpful for the construction of more compact and lower cost desktop AMS equipment for meeting the growing demand for scientific research and sample measurement.