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MS 10.7: Vortrag
Donnerstag, 12. März 2020, 12:30–12:45, f128
Developments towards the detection of 135Cs and 137Cs by AMS — •Alexander Wieser1, Johannes Lachner1,2, Martin Martschini1, Peter Steier1, Alfred Priller1, Maki Honda1, Oscar Marchhart1, and Robin Golser1 — 1University of Vienna, Faculty of Physics - Isotope Physics, Austria — 2HZDR, Dresden
The isotopic ratio 135Cs/137Cs can be used to assign sources of anthropogenic cesium, as a geochemical tracer, or for modifying dispersion models. Due to its long half-life, 135Cs is hard to detect via decay counting.
Mass Spectrometry has to deal with isobaric interferences of the stable 135Ba and 137Ba for Cs detection. The new method of Ion Laser InterAction Mass Spectrometry (ILIAMS) at the Vienna Environmental Research Accelerator (VERA) overcomes this problem by exploiting differences in the electron affinites of CsF2− and BaF2− molecules.
A 133CsF2− current on the order of 100 nA from a mixed Cs2SO4 and PbF2 - matrix is extracted from the ion source. The sample material is mobilized by heating the ionizer only, so no external sputtering material is needed. First results show reproducible detection of 135Cs and 137Cs in in-house reference materials. With 1 mg stable Cs carrier, we reach a blank level of 137Cs/133Cs=6· 10−12, which corresponds to ≈ 30 mBq. We aim to further improve this value by at least two orders of magnitude for measuring environmental samples.