Optimizing 10Be measurements at AMS systems with less than 300 kV terminal voltage

AMS measurements of 10 Be have been the domain of conventional AMS systems with terminal voltages of 3 MV or higher. However, low energy AMS systems operating at terminal voltages of less than 300 kV offer substantial potential for 10 Be analysis. We describe the M ulti I sotope L ow E nergy A MS System (MILEA), a novel AMS system based on a 300 kV vacuum insulated HV platform for its performance of 10 Be measurements. Charge exchange processes, molecular break-up reactions, as well as ion detection and identification processes are discussed. Charge state distribution measurements reveal an unexpected increase of the Be 2+ charge state yield below 200 keV ion energy which is not observed for B 2+ ions of the same energy. This increases overall detection efficiencies and enhances isobar suppression. The coulomb explosion at lower energies of the injected BeO − ion during the stripping process causes increase energy spread in addition to the energy loss straggling. This results in additional tailing of the ion beam during transport through subsequent dispersive beam optical elements. Nevertheless, the presence of a SiN degrader foil positioned after charge state analysis in combination with optimized gas ionization detectors offers sufficient isobar suppression capability to acieve background levels well below 5x10 −15 . Tests of the system under routine operation conditions using accepted AMS 10 Be standards show the high reproducibility and demonstrate the excellent performance of the system.