AMS of C-14 at low energies

At the ETH/PSI AMS facility C-14 test measurements have been performed at low terminal voltages of 0.5 and I MV in order to study the feasibility of AMS with very small accelerators. These experiments have demonstrated that molecules ((CH)-C-13 and (CH2)-C-12) in charge states 1(+) and 2(+) can be destroyed in an Ar gas stripper reducing their intensities by at least ten orders of magnitude at a stripper thickness of about i mu g/cm(2). It could be shown that particle identification and separation of (CH2)-C-12 and N-14 from C-14 is possible with a Delta E-E gas counter for an energy of 3 MeV (using charge state 2(+) at 1 MV terminal voltage). A Si detector combined with a time-of-flight system was used for the experiments at 1 MeV, At both energies background has been found at levels below 10-(13). This is certainly sufficient for biomedical applications. For C-14 dating, further background reduction is required.