Freiburg 2024 – wissenschaftliches Programm
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.