SAMOP 2023 – scientific programme

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MS: Fachverband Massenspektrometrie

MS 1: Accelerator Mass Spectrometry I

MS 1.5: Talk

Tuesday, March 7, 2023, 12:15–12:30, F128

Improving the ¹⁰Be detection efficiency with DREAMS — •Johannes Lachner, Carlos Vivo Vilches, Dominik Koll, Georg Rugel, Konstanze Stübner, and Anton Wallner — Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Accelerator Mass Spectrometry & Isotope Research

¹⁰Be measurements presently take up the largest fraction of the DREAMS (DREsden AMS) beamtimes at the 6 MV accelerator of HZDR. We investigated the advantages of increasing the accelerator terminal voltage in order to improve the ¹⁰Be counting efficiency. Stripping of the BeO⁻ ions extracted from the ion source to Be²⁺ is done using Ar stripper gas at a gas density below the level required for an equilibrium charge state distribution. The positive ions are directed towards a 1 µm thin silicon nitride foil that helps to suppress the ¹⁰B interference by differential energy loss and separation in the following electrostatic analyser. After passage through the absorber foil the mean charge state of Be ions is increased and the 4+ charge state is selected and transported to the detector. Because of the higher ion energy, the yield for this charge state gets higher and the efficiency of ¹⁰Be measurements is improved with higher terminal voltage.

At 5.8 MV terminal voltage ca. 32.5% of the ¹⁰Be extracted from the ion source are transported to the detector compared to 23% at the previous setting of 4.5 MV. We furthermore present data of samples with known B concentration and give values for the ¹⁰B suppression related to the different effects of separation, via the energy loss and via the gas ionization chamber.