10Be and 26Al low-energy AMS using He-stripping and background suppression via an absorber

The transmission of the ion beam through a tandem accelerator is a critical parameter for efficient detection of long-lived radionuclides by sensitive accelerator mass spectrometry (AMS). With beam energies at the accelerator terminal of less than 600 key, high transmissions are obtained using He as stripper gas. Here, we discuss Be, B, and Al transmissions in view of their application in the AMS determination of the long-lived radioisotopes Be-16 and Al-26 with compact facilities. The charge state 2+ of Al and Be shows a high yield, but in both cases an intense background from other nuclides has to be handled. The applicability of a combination of an absorber cell with a gas ionization chamber was tested for suppression of the main background for Be-16(2+) (B-10(2+)) and Al-26(2+) (C-13(1+)). Energy loss simulations of the involved nuclides confirm the performance observed in the experiments. The findings concerning He stripping and detection methods at low energies may allow the construction of very compact AMS setups for light isotopes. (C) 2014 Elsevier B.V. All rights reserved.