Freiburg 2024 – wissenschaftliches Programm

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MS: Fachverband Massenspektrometrie

MS 3: Accelerator Mass Spectrometry I

MS 3.3: Vortrag

Dienstag, 12. März 2024, 11:45–12:00, HS 3042

Upgrade of the silicon nitride absorber for ¹⁰Be AMS at VERA — •Carlos Vivo-Vilches, Peter Steier, Martin Martschini, Silke Merchel, and Robin Golser — University of Vienna, Faculty of Physics, Austria

Suppression of ¹⁰B in accelerator mass spectrometry of ¹⁰Be at VERA is provided by a stack of silicon nitride foils placed in front of a gas ionization chamber. A nominal thickness of 6700 nm is just enough to stop ¹⁰B ions, while letting ¹⁰Be ions reach the detector. This avoids the ¹⁰Be losses of the degrader foil technique used in the past, arising from angular scattering and the different charge states after the foil, increasing the detection efficiency. A disadvantage of the foil stack setup until now was the fixed thickness of the foils once the setup is inside the beamline. More generally, the background caused by products from the nuclear reaction of ¹⁰B with the ¹H present in the foils, ¹H(¹⁰B,α)⁷Be, makes it challenging to reach similar ¹⁰Be/⁹Be blank ratios as with the degrader foil technique.

Recently, a rotatable silicon nitride foil with a thickness of 1200 nm was installed in front of the foil stack, allowing adjustments in the total thickness for optimization of the ¹⁰B suppression and ¹⁰Be transmission. Besides, it also improves discrimination of the ⁷Be background. The size of each foil and their distances to the detector have also been studied in simulations and experimentally in order to decrease the angular acceptance of ⁷Be ions without significantly losing ¹⁰Be ions. In this talk we will present first results on the efficiency, reproducibility and the blank value achieved with this setup.