Hannover 2020 – wissenschaftliches Programm
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MS 8.2: Vortrag
Mittwoch, 11. März 2020, 15:00–15:15, f128
Increased ionization efficiency for the detection of 236U and 233U by AMS — •Michael Kern, Karin Hain, Maki Honda, Peter Steier, Andreas Wiederin, and Robin Golser — University of Vienna, Faculty of Physics - Isotope Physics, Austria
The 233U/236U ratio is a promising method for contamination source assessment. The detection of 233U is most critical due to its abundance ranging below 10−12, where the Vienna Environmental Research Accelerator (VERA) is to date the only instrument delivering sufficient detection efficiency for routine measurements of environmental samples. The ionization efficiency is the main limiting factor (≈ 10−4). Introduction of a new preparation method for samples containing ≈ 5 µg U extracted as UF5− within PbF2 + Fe2O3 matrix instead of UO− sputtered from Fe2O3 yields a strong improvement in detection efficiency by up to a factor 10. Thus substantially shortened measurement duration could be obtained, while maintaining the same statistical uncertainty. We also succeeded in further cutting down hydrides of highly abundant adjacent masses (232ThH3+, 235UH3+) at lower He stripper gas pressure, which results in a further improvement of efficiency. This presentation will give detailed insights on the new sample preparation as well as ion current characteristics and method verification.