22-27 September 2019
Trade Fairs and Congress Center (FYCMA)
Europe/Madrid timezone

Radioargon Dating with Atom Trap Trace Analysis

24 Sep 2019, 16:00
Trade Fairs and Congress Center (FYCMA)

Trade Fairs and Congress Center (FYCMA)

Av. de José Ortega y Gasset, 201 29006 Malaga, Spain
Poster Topic 5 - Tools, methods and models to study groundwater Poster with refreshments


Mr Amin Tong


Amin. L. Tong, Ji-Qiang Gu, Wei Jiang, Zheng-Tian Lu,
Florian Ritterbusch, Guo-Min Yang
University of Science and Technology of China (USTC).
CAS Center for Excellence in Quantum Information and Quantum Physics
Hefei National Laboratory for Physical Sciences at the Microscale.
Email: amin@mail.ustc.edu.cn

The noble gas radioisotope 39Ar (half-life = 269 yrs.) is the only reliable dating isotope for water and ice in the range of 50-1,400 years, a time range particularly important for tracing ocean circulation, groundwater and alpine glacier ice [3]. However, its use especially in oceanography has been hampered by the large sample size required by Low-Level Counting, so far the only available detection technique for 39Ar.
Atom Trap Trace Analysis (ATTA) is a laser-based atom counting method with ultra-high selectivity and sensitivity that has been developed for analyzing the environmental isotope tracers 85Kr and 81Kr [1]. Its realization for 39Ar presents a major challenge due to its extremely low abundance of only 8×10^(-16) [2], which is more than 800 times lower than for 81Kr. The applicability of ATTA to 39Ar has been demonstrated in a proof-of-principle experiment [4]. Practical dating of groundwater and ocean samples could later be demonstrated with 39Ar count rates reaching up to 7 atoms/h [5, 6].
Here, we present the latest status of the ATTA system for 39Ar at the USTC. We currently achieve an atmospheric 39Ar count rate of 10 atoms/h. In order to obtain a higher 39Ar count rate, together with the Institute of modern physics in Lanzhou we are working on 39Ar pre-enrichment. In preliminary tests, we could demonstrate an enrichment by a factor 10. We plan to test the water samples in a few months.

Keywords: Laser, Argon, Isotope Trace
Presentation Type: Poster
[1] C. Y. Chen, Science 286, 1139 (1999).
[2] Loosli, H., A dating method with 39Ar, Earth Planet. Sci. Lett., 63(1), 51–62 (1983).
[3] Z.-T. Lu, P. Schlosser, W.M. SmethieJr., N.C. Sturchio, T.P. Fischer, B.M. Kennedy, R. Purtschert, J.P. Severinghaus, D.K. Solomon, T.Tanhua, R. Yokochi. Earth-Science reviews 138, 196 (2014).
[4] W. Jiang, W. Williams, K. Bailey, et al. 39Ar detection at the 10−16 isotopic abundance level with Atom Trap Trace Analysis. Phys. Rev. Lett., 106,103001 (2011)
[5] F. Ritterbusch, S. Ebser, J. Welte, et al. Groundwater dating with Atom Trap Trace Analysis of 39Ar. Geophysical Research Letters, 41, 6758-6764, (2014)
[6] S. Ebser, A. Kersting, T. Stöven, et al. 39Ar dating with small samples provides new key constraints on ocean ventilation. Nat. Commun. 9, 5046, (2018)

This study is supported by National Key Research and Development Program of China (2016YFA0302200), by National Natural Science Foundation of China, NSFC (41727901).

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