New concepts of 10Be AMS at low energies

Isotopic ratios of 10Be/9Be with a background sensitivity of 2×10−14 can now be measured with the 0.6MV Tandem accelerator of PSI/ETH Zurich using BeF2 instead of BeO as sample material and injecting BeF− to suppress the boron detector count rate. A new, high-resolution gas ionization detector with a thin silicon nitride entrance window and special preamplifier design are essential in order to achieve this sensitivity. A particle transmission of 50% is possible for charge state 1+. Due to the maximum count rate that can be accepted by the detector the BeF− currents are limited to a few hundred nA.