München 2004 – scientific programme

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MS: Massenspektrometrie

MS 4: Beschleunigermassenspektrometrie (Entwicklung)

MS 4.2: Talk

Monday, March 22, 2004, 17:45–18:00, HS 112

Accelerator Mass Spectroscopy of ¹⁰Be using BeF⁻ — •Michal Grajcar¹, Max Döbeli², Peter W. Kubik², Hans A. Synal², Lukas Wacker¹, and Martin Suter¹ — ¹Institute for Particle Physics, ETH Hönggerberg, CH-8093 Zürich, Switzerland — ²Paul Scherrer Institut (PSI), c/o Institute for Particle Physics, ETH Hönggerberg, CH-8093 Zürich, Switzerland

¹⁰Be is one of the most important long-lived cosmogenic radioisotopes in environmental research and has many dating and tracer applications. A new method is described by which ¹⁰Be can be measured with compact AMS systems.

BeF targets were prepared and analysed with an AMS facility operating at 0.6 MV terminal voltage. Selecting the charge state 1⁺, the particle transmission through the accelerator is about 40% and a final energy for ¹⁰Be of 0.8 MeV is obtained. The extraction of ¹⁰BeF⁻ instead of ¹⁰BeO⁻ from the ion source has the advantage of reducing ¹⁰B intensities in the beam by about 5 orders of magnitude. A high energy resolution ΔE-E_R gas ionisation counter was used for the final identification. This detector allows additional boron suppression by more than 5 orders of magnitude. Thus, in total, boron is suppressed by at least 10 orders of magnitude and a measured ¹⁰Be/⁹Be background ratio is below 10⁻¹⁴.

Successful measurements of environmental samples demonstrate the potential of the new method.