Opportunities and limits of AMS with 3-MV tandem accelerators

With the Vienna Environmental Research Accelerator (VERA, based on a 3-MV tandem accelerator) we have systematically explored the limitations due to terminal voltage, both by modelling and by experiments. If no stable atomic isobars exist, e.g. for 236U or 244Pu, the same detection limits as for large machines have been achieved. In cases where isobar separation is required, the achievable energy is the limitation. To study isobar separation experimentally, we use a new method called ΔTOF: the different energy loss in a foil is measured with a time-of-flight (TOF) detector. Separation of 36Cl from 36S is possible. With diamond like carbon (DLC) stripper foils (0.6 μg/cm2) and by pushing our Pelletron tandem to 3.6 MV, we achieved a significant increase in energy compared to gas stripping at 3 MV: e.g. 36Cl7+ at 28.8 MeV instead of 36Cl5+ at 18 MeV can be used.