Ultra-Trace Plutonium Detection

This paper describes the performance of a multi-collector thermal ionization isotope ratio magnetic sector mass spectrometer. Using a unique ion dispersion lens the mass dispersed individual isotope beams are separated sufficiently to allow a full-sized discrete dynode pulse counting multiplier to be used to measure each isotope beam. SRM 996 (244Pu spike) at loadings of 2.4 and 12 fg on resin beads and the Pu separated fraction of SRM 4350B Columbia River Sediment samples were measured. The limit of detection (3σ) for 240Pu was 3.4 attograms; the limit of quantitation (10σ) was 11.2 attograms.