Beryllium-7 at DREsden Accelerator Mass Spectrometry

Half-lives of routine accelerator mass spectrometry (AMS) nuclides typically range from thousands to millions of years. We measured short-lived ⁷Be (T1/2 = 53.2 d) at the DREsden AMS-facility (DREAMS) [1] as low as 90 mBq, which can be challenging for rapid γ-counting. Simultaneous determination of ⁷Be and ¹⁰ Be (T_1/2= 1.387 Ma) via AMS is advantageous for improved understanding of production, transport, and deposition of atmospherically produced ^7,9,10Be [2].
Data was normalized to a ⁷ Be sample produced via ⁷Li(p,n)⁷Be, measured by γ-counting and chemically processed to BeO after adding low-level ⁹Be carrier (⁷Be/⁹Be ≈ 10^-12). The isobar ⁷Li is completely eliminated by chemistry and the degrader foil technique (at detector ⁷Be⁴⁺, 10.2 MeV, no ⁷Li⁴⁺ possible). The blank ratio of 5 × 10^{-16 7}Be/⁹Be (0.8 mBq) and simple and fast chemistry allows for the measurement of rainwater samples, collected in Germany, as small as 10 mL corresponding to a few times 10^{-14 7}Be/⁹Be [3,4].
Thanks to D. Bemmerer (HZDR) and G. György (ATOMKI, Hungary) for help with the ⁷Be normalization material.
[1] G. Rugel et al., NIMB 370 (2016) 94.
[2] A.M. Smith et al., NIMB 294 (2013) 59.
[3] R. Querfeld et al., JRNC 314 (2017) 521.
[4] C. Tiessen et al. JRNC (to be submitted).