Hannover 2020 – scientific programme

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MS: Fachverband Massenspektrometrie

MS 8: Accelerator Mass Spectrometry and Applications I

MS 8.2: Talk

Wednesday, March 11, 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.