Hannover 2010 – wissenschaftliches Programm

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MS: Fachverband Massenspektrometrie

MS 8: Poster

MS 8.1: Poster

Donnerstag, 11. März 2010, 16:00–18:00, Lichthof

An optimized ion-optical setup for AMS of ¹⁰Be with a degrader foil — •Martin Martschini, Oliver Forstner, Robin Golser, Walter Kutschera, Leonard Michlmayr, Alfred Priller, Peter Steier, and Anton Wallner — VERA Laboratory, Universität Wien - Fakultät für Physik - Isotopenforschung, Austria

The challenge in accelerator mass spectrometry (AMS) of ¹⁰Be (t_1/2=1.4 Ma) is the suppression of the stable isobar ¹⁰B. One method established in recent years at VERA (Vienna Environmental Research Accelerator), is the use of a thin degrader foil to introduce an energy difference between ¹⁰Be and ¹⁰B, followed by an additional energy-sensitive bending element and a split-anode ionization chamber. While this setup has considerably reduced our background (¹⁰Be/⁹Be < 10⁻¹⁵), it initially suffered from a poor transmission after the degrader foil.

In order to optimize our setup, we have measured the phase space of a ⁹Be²⁺-beam and determined the transverse emittance and energy distribution of the beam. These results were used in ion-optical simulations of our high energy beamline. They allowed to identify the beamline elements responsible for transmission losses and helped to plan modifications of our quadrupole doublet and the switcher magnet chamber. Thereby, the transmission increased by a factor of 3. At VERA, the degrader foil method now clearly outperforms other established methods for samples with ¹⁰Be/⁹Be ratios lower than 10⁻¹³.