Lisa Cousins

A design study for the analysis of 90Sr And 135,137Cs by ISA-AMS

Extending the range of Accelerator Mass Spectrometry (AMS) to the fission products 90Sr and 135,137Cs would offer numerous advantages for non-proliferation surveillance activities. A new method for suppressing the interfering isobars 90Zr (and 90Y) and 135,137Ba using low kinetic energy (<20 eV) gas-phase reactions in an AMS injection line can help achieving this goal in a cost effective way [1]. The reactions occur in a radiofrequency quadrupole (RFQ) cell filled with a low pressure gas, part of a device known as the Isobar Separator for Anions (ISA). Combined with fluoridematrix assisted ionization, this method greatly improves the analytical capabilities of AMS for 90Sr and will enable the direct analysis of 135,137Cs below sub-parts per trillion levels. The ISA alone provides interference suppression factors of 4×10−6 for ZrF3−/SrF3− and 2×10−5 for BaF2−/CsF2−. The general performance improvement provided by the ISA, however, critically depends on the capacity of this device to transmit the wanted ani...