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Contaminant Analysis of Polycrystalline and Single Crystal Niobium Used in Accelerator Cavities

Secondary Ion Mass Spectrometry (SIMS) can characterize the surface and near surface of Nb used in accelerator cavities. Results show Nb oxide in the 2-3 nm range, a depleted H concentration in the oxide compared with the bulk, and N, C, O lower in an annealed single crystal sample than several polycrystalline samples. Other metallic contaminants are primarily at the surface, but tantalum is distributed uniformly through the material.