Freiburg 2024 – wissenschaftliches Programm
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MS: Fachverband Massenspektrometrie
MS 9: Accelerator Mass Spectrometry IV
MS 9.3: Vortrag
Freitag, 15. März 2024, 11:45–12:00, HS 3042
Isobar suppression and normalization methods for ultra-trace analysis of Tc-99 — •Stephanie Adler1, Karin Hain1, Martin Martschini1, Stefan Pavetich2, Steve G. Tims2, L. Keith Fifield2, Dominik Koll2, and Robin Golser1 — 1University of Vienna, Faculty of Physics, Austria — 2Australian National University, Research School of Physics, Australia
Determination of absolute concentrations of the anthropogenic radionuclide 99Tc (t1/2=2.1 × 105 yr) in environmental samples by AMS requires suppression of the stable isobaric background of 99Ru and a reliable normalization method. At the Vienna Environmental Research Accelerator (VERA), isobar suppression is addressed with Ion-Laser InterAction MS (ILIAMS). It was shown that RuF5− can be suppressed by a factor of up to 105 using a 532 nm-laser, making extraction of 99TcF5− a viable option for ILIAMS. For normalization to NbF5− extracted from the same sample, the reproducibility of the method was significantly improved from 50% to 15% by optimization of ion source parameters. Without ILIAMS, the separation of 99Ru from 99Tc is currently only possible at the AMS facility at the Australian National University (ANU), using ion energies of up to 190 MeV. There, TcO− extraction and normalization to the 93Nb-current showed a reproducibility of 15%. 99Ru and 99Tc are separated in an 8-anode ionization chamber owing to minute differences in their energy loss characteristics, observable only at highest ion energies. This method yielded a Ru suppression factor of 8000, and recent investigations showed a potential improvement by using an additional SiN degrader foil stack.
Keywords: Technetium-99; Ion-Laser Interaction Mass Spectrometry; Isobar Suppression; Normalization Methods