Determination of isotopic composition of uranium in the CMX-4 samples by SIMS

From the 16 laboratories participating in CMX-4, three laboratories (Buonarroti, Matisse, and Pollock) have utilized secondary ion mass spectrometry (SIMS) for the characterization of the samples. SIMS allows analysis of samples on micrometric scales and thus it can be used for the analysis of individual particles. The aim of the SIMS analysis was to identify any possible heterogeneity of isotopic composition of the uranium, and to make a quantitative characterization of this heterogeneity to look for unique identifiers of the material. The outcome of the SIMS analysis from the three laboratories is described and discussed in this paper.