Erlangen 2022 – scientific programme
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MS: Fachverband Massenspektrometrie
MS 4: Accelerator Mass Spectrometry
MS 4.6: Talk
Wednesday, March 16, 2022, 12:00–12:15, MS-H9
Improved 41Ca AMS measurements at DREAMS — •Carlos Vivo-Vilches, Georg Rugel, Johannes Lachner, Anton Wallner, Dominik Koll, Konstanze Stuebner, Sebastian Fichter, and Stephan Winkler — Helmholtz-Zentrum Dresden-Rossendorf, AcceleratorMass Spectrometry and Isotope Research, Dresden, Germany
Sensitivity of 41Ca measurements at the 6 MV AMS system at HZDR, DREAMS, using calcium fluoride (CaF2) targets, is mainly limited by 2 factors: the total efficiency of the measurements; and the fraction of ions of its isobar 41K which mimic the signal of 41Ca in the gas ionization chamber detector.
The addition of lead fluoride (PbF2) to the target mixture has been proven to boost the production of different (MFn)- ions. At DREAMS, changing the previously used mixture of CaF2+Ag (1:4 w/w) by CaF2+Ag+PbF2 (1:4:4 w/w), ionization efficiency is increased from ∼0.15% to ∼0.45%.
The 41K suppression by the detector can also be improved, even without changes in the instrumentation itself. With an optimized analysis of the 4-dimensional signals from the gas ionization chamber detector, the suppression factor can be increased, at least, a factor 2: from 2 × 104 to 4 × 104.
The reported changes improve the total efficiency of 41Ca detection as well as the suppression of the 41K isobar and lead to a 41Ca/40Ca sensitivity of 2-3 × 10-15 with an overall efficiency of ∼0.03%.