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MS 10.8: Vortrag
Donnerstag, 12. März 2020, 12:45–13:00, f128
AMS of 90Sr at the sub-fg-level using laser photodetachment at VERA — •Oscar Marchhart1, Martin Martschini1, Maki Honda1, Dag Hanstorp2, Johannes Lachner1,3, Haimei Liang2, Alfred Priller1, Peter Steier1, Alexander Wieser1, and Robin Golser1 — 1University of Vienna, Faculty of Physics-Isotope Physics, Austia — 2University of Gothenburg, Department of Physics, Sweden — 3HZDR, Dresden
The fission product 90Sr (T1/2 = 28.9 a) is of interest in environmental sciences for its radiotoxicity as well as a potential tracer. Limits of detection (LoD) of mass spectrometric methods such as ICP-MS, RIMS or conventional AMS are close to the radiometric limit of 3 mBq.
The main problem in AMS of 90Sr is the strong interference of the stable isobar 90Zr. This problem can be overcome with the new Ion Laser InterAction Mass Spectrometry (ILIAMS) setup at the Vienna Environmental Research Accelerator (VERA). It provides near complete suppression of elemental or molecular isobars via selective laser photodetachment inside a gas-filled radiofrequency quadrupole (RFQ). With 10 W of laser power from a 532 nm cw-laser and a He + O2 mixture as buffer gas, ILIAMS achieves a suppression factor for 90Zr of 107. Extracting SrF3− out of the ion source and elemental separation inside an ionization chamber gives an additional Zr suppression of 105. Measurements with dilution series of reference materials were successfully conducted. The overall Sr detection efficiency is 0.4 and the blank level 90Sr/Sr =(4.5 ± 3.2)×10−15. This corresponds to a more than tenfold improved LoD of 0.1 mBq.