10Be measurements with terminal voltages below 1 MV

Abstract

At the AMS laboratory in Zurich, the potential for 10Be detection is presently being explored with the existing 1-SDH Pelletron facility. Using charge state 2+, an energy of about 1.5 MeV and a transmission of about 13% is obtained. The standard absorber technique is not well suited to reduce the 10Be rate before the detector, because the range straggling at these low energies is significant. Therefore, a dE/dx-foil technique has been tested. A stack of 7 carbon foils (20 μg/cm2 total) has been placed between the high-energy analysing magnet and the electrostatic deflector. With this technique, a boron reduction of about 3 orders of magnitude has been achieved. A gas ionisation chamber was installed at the end of the AMS beam line with which the boron background has been suppressed by another 5 orders of magnitude. The total background suppression is therefore at least 8 orders of magnitude. Applying standard chemical procedures the background level is equivalent to a 10Be/9Be-ratio of about 10−12.