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MS: Fachverband Massenspektrometrie

MS 7: Accelerator Mass Spectrometry and Applications I

MS 7.4: Vortrag

Donnerstag, 3. März 2016, 12:00–12:15, f128

Improved ²⁶Al measurements with absorber setup at low energies — •Klaus-Ulrich Miltenberger, Marcus Christl, Arnold Milenko Müller, Hans-Arno Synal, and Christof Vockenhuber — Laboratory of Ion Beam Physics, ETH Zurich, Otto-Stern-Weg 5, 8093 Zurich, Switzerland

At the ETH 500 kV AMS facility (Tandy) transmission of more than 50% is achieved for aluminium ions in charge state 2+, enabled by the use of helium as a stripper gas in the accelerator. However, to utilize the high transmission for sensitive AMS measurements of ²⁶Al, the intense interference caused by ¹³C¹⁺ entering the detector has to be suppressed. To achieve this, a new absorber setup for low energy ²⁶Al²⁺ measurements was developed and tested.

Using the new absorber-detector configuration, several standards, blanks, and real samples were measured. Compared to earlier measurements conducted at the ETH 6 MV accelerator, the statistical measurement errors could be reduced significantly due to better counting statistics and more stable measurement conditions. The ²⁶Al/²⁷Al ratios measured for different standards (ZAL94N, Nishiizumi) correspond very well with their nominal ratios ranging from 5 · 10⁻¹³ to 5 · 10⁻¹⁰. Blank ratios are currently in the range of 1−3 · 10⁻¹⁴ and limited by ²⁶Al cross-contamination in the SNICS ion source caused by the high ratio ((480 ± 18) · 10⁻¹²) of the ZAL94N standard. To minimize cross-contamination the new ETH Zurich standard ZAL02 with a nominal ²⁶Al/²⁷Al ratio of (46.5 ± 0.1) · 10⁻¹² was introduced.