Advanced instrumentation for accelerator mass spectrometry

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The advantages of accelerator mass spectrometry (AMS), in which isotopes and rare atoms can be measured in sub-milligram samples with sensitivities approaching 1 part in a thousand million million, have been largely confined to elements which readily make negative ions and which have isobars that do not, such as Carbon-14 and Iodine-129. For elements that do not meet one or both of these conditions, the development of analytical strategies has been limited and often been confined to the use of larger accelerators (>5 MV). Two innovations begun recently at the IsoTrace Laboratory have demonstrated that the use of AMS can be extended to a much larger fraction of the periodic table. These are: (i) the use of fluoride molecular anions to enhance the production of the negative ions 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 - collectively known as the Isobar Separator for Anion (ISA).