Advanced Instrumentation for Research in Accelerator Mass Spectrometry

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Accelerator mass spectrometry (AMS) is a technology used to measure concentrations of rare atoms or isotopes in milligram samples with sensitivities as high as 1 part in 1015 (thousand million million). Such measurements are generally limited to elements which readily make negative ions (anions) and for which anions of other elements with the same mass (isobars) do not exist, e.g. 14C and 129I. If atomic isobars do exist, measurements require the use of larger accelerators (>5 MV) and tedious sample preparation chemistry. Two innovations begun at the IsoTrace Laboratory (Toronto), shortly before it was closed, provided the groundwork needed for the extension of AMS to a much larger fraction of the periodic table. These are: (i) the use of fluoride molecular anions to increase the production of the anions required for AMS and (ii) the use of radio-frequency quadrupole ion guides in cooling and reaction cells to eliminate both atomic and molecular isobars at very low energies - for which a prototype system, the Isobar Separator for Anion (ISA) has been developed and patented.***The primary and long-term goal of this research is to more fully understand the physical (and some chemical) processes which make this equipment work, but which seem to limit its further development. This understanding will be tested by formulating new procedures and components, which, when successful, will become part of future AMS systems. The commissioning of the A. E. Lalonde AMS Laboratory at the University of Ottawa, and the incorporation of recently developed equipment from IsoTrace, provide a unique opportunity to deepen that understanding, to develop new techniques based on this knowledge and to explore the many new applications which they enable. The near-term research program will include:***a) investigating new phenomena observed in earlier work on the ISA. These include the necessity to control the energy and position of the ions, the search for reaction gases with states to which electrons can be resonantly transferred and the determination of the structure of the analyte, isobar or reaction gas molecules. ***b) investigating processes in the formation of fluoride anions. New methods for generating larger molecular anion beams were recently discovered using the high current ion sources at the Lalonde Lab, but these processes are not yet understood. ***c) re-starting the gas ion source research, delayed by the IsoTrace closing. This is motivated by the need of many scientists to analyze compound-specific (hence smaller) 14C samples with the eventual extension of this capability to tritium and 129I measurements, and ***d) continuing collaboration with researchers using AMS to support their work in diverse fields such as tracing pollutant pathways, determining chronologies for geological processes, enabling nuclear forensic investigations, testing new pharmaceuticals and monitoring aspects of human health.