Boron suppression with a gas ionization chamber at very low energies (E < 1 MeV)

Efficient boron suppression for precise 10Be measurements with AMS is crucial. The performance of ΔE − Eres gas ionization chambers is also very important for isobar suppression at low beam energies (<1 MeV). A boron suppression of 6–7 orders of magnitude is achievable with the ETH ΔE − Eres gas ionization in the standard operational mode (readout of ΔE and Eres electrodes). Some physical effects such as pulse height defect or the energy focusing effect within a ΔE section will be discussed, emphasizing 10Be measurements below 1 MeV. Additionally the potential of silicon nitride membranes as passive energy degraders in front of the detector is demonstrated.