~(10)Be AMS measurements at low energies (E < 1 MeV)

摘要

The longlived isotope ~(10)Be is of great importance in earth sciences for dating applications, reconstruction of the solar activity or in climate research. Routine AMS measurements with BeO samples are performed on accelerators with a terminal voltage above 2 MV. Applying the degrader foil technique for boron suppression, first tests with BeO samples on the 0.6 MV ETH/PSI machine were limited by background to a ~(10)Be/~9Be ratio of 10~(13). The background was identified as ~9Be which reaches the detector by scattering processes. By applying an additional magnetic mass filter to the high energy mass spectrometer the background was effectively removed. A ~(10)Be/~9 Be background ratio of <5 x 10~~(15) was achieved. The overall efficiency (detected ~(10)Be compared to BeO~- injected into the accelerator) was 7-8%.