Ultrasensitive (<1 mBq), cheap, and fast detection method for ⁷Be allowing high sample throughput

Beryllium-7 (T_1/2 = 53.22 d), mainly measured via γ-spectrometry, is used as a (natural) radiotracer for education and science [1]. For activities < 0.1 Bq and especially for samples also containing so longer-lived ¹⁰Be (T_1/2 = 1.387 Ma), accelerator mass spectrometry (AMS) is the method-of-choice.
We demonstrate that ⁷Be and ¹⁰Be can be quantified at the DREsden AMS (DREAMS) facility [2,3] on the same prepared BeO. Detection limits (⁷Be) are as low as ~ 0.6 mBq, hence, one-to-two orders of magnitude better than “standard/ordinary” and “sophisticated” decay counting (e.g. in an underground laboratory). Uncertainties for small samples are usually 6-7 % for small samples. The method is validated by γ-counting of two larger rainwater samples showing an excellent agreement with the AMS result [4].
Samples as small as tens of millilitres of rainwater can be chemically processed (after acidification) within a few hours without expensive and time-consuming ion exchange. Isobar (⁷Li) suppression by chemistry and AMS is sufficient to guarantee an ultrasensitive, cheap, and fast detection method for ⁷Be allowing high sample throughput.
The DREAMS facility allows external user access free-of-charge via a proposal system. Further information can be found at www.hzdr.de/ibc or www.ionbeamcenters.eu.

Acknowledgments
Parts of this research were carried out at the Ion Beam Centre (IBC) at the Helmholtz-Zentrum Dresden-Rossendorf e. V., a member of the Helmholtz Association. We appreciate support of Dominik Güttler, René Ziegenrücker and the DREAMS operator team during AMS-measurements, of Gyürky György (Hungarian Academy of Sciences) for providing ⁷Be for the calibration material, and of BMBF (05K16MG1) and DAAD-RISE Professional (HZDRPH-456) for funding. It was a pleasure to discuss ⁷Be-AMS with Andrew Smith (ANSTO).

References
[1] R. Querfeld, S. Merchel, G. Steinhauser, J. Radioanal. Nucl. Chem. 314 (2017) 521-527.
[2] S. Akhmadaliev et al., Nucl. Instr. Meth. B 294 (2013) 5-10.
[3] G. Rugel et al., Nucl. Instr. Meth. B 370 (2016) 94-100.
[4] C. Tiessen et al., Accelerator mass spectrometry (AMS) for beryllium-7 measurements in smallest rainwater samples, J. Radioanal. Nucl. Chem, 2019, doi: 10.1007/s10967-018-6371-6.