Preliminary results of positive ion mass spectrometry based on a 2.45 GHz ECR ion source and a non-metallic gas target

• Published in: Journal of physics. Conference series Vol. 2244; no. 1; pp. 12093 - 12097
• Main Authors: Li, K., Peng, S.X., Ma, T. H., Wu, W.B., Jiang, Y. X., Cui, B.J., Zhang, A. L., Sun, J., Guo, Z. Y., Chen, J. E.
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.04.2022
• Subjects: Charge efficiency; Charge exchange; Ethylene; Ion sources; Ions; Isobars; Mass spectrometry; Negative ions; Permanent magnets; Physics; Positive ions; Radiometric dating; Scientific imaging; Spectroscopy
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/2244/1/012093

Abstract Positive-ion mass spectrometry (PIMS) is a positive-to-negative ion conversion metrology that just operated on the opposite of traditional accelerator mass spectrometry (AMS) on high-precision radiocarbon dating. With a higher efficient simple structure plasma ion sources instead of AMS sputter ion sources, lower ion energy (tens keV) in place of MeV, and limited footprint facility, PIMS will be a powerful competitor to AMS in the future. To precisely measure 14 C, interference of molecular isobars (such as 12 CH 2 , 13 CH) will be eliminated with higher charged ions (charge state ≥ 3; molecular cations 12 CH 2 2+ is metastable, can be eliminated by higher stripping pressure.), nitrogen will be eliminated inside the charge-exchange cell (CXC) through charge exchanging with target gas. To demonstrate the probability of PIMS with a 2.45 GHz ECR ion source, an experiment was launched at Peking University (PKU). A compact permanent magnet 2.45 GHz ECR ion source is designed to produce carbon ions from CO 2 . A CXC unit was installed after the extraction system and ethylene is chosen as charge exchange gas. Preliminary experiments prove that more than hundreds of microamp of C 2+ beam can be produced with this ECR source. By injecting ethylene into CXC, several microamp C - beam was detected and the C 2+ ions charge exchange efficiency to C - ions can reach close to 5%.