CLAS: NanoSIMS Facility

This latest generation of secondary-ion mass spectrometer has a co-axial design with normal primary ion incidence and secondary ion extraction. The design reduces the working distance between the extraction lens and sample surface to 400μm, resulting in small beam sizes and high ion collection efficiency. The high spatial resolution (~50nm for Cs+ beam and ~200nm for O−) differentiates the NanoSIMS from other SIMS instruments. High transmission at high mass resolution (e.g., 70% relative transmission at a mass resolving power of 6000), essential for the analyses of small volumes, is achieved by an electrostatic analyzer, a magnetic sector (650mm radius magnet) and optimized transfer optics configuration. Up to seven ionic species can be collected simultaneously from the same sputtered volume through multicollection by either electron multipliers or Faraday cups. Multicollection in conjunction with magnetic-field peak-jumping can also be performed to measure more than seven species. Relatively precise measurements (~several ‰ (2σ) for O, S and Mg isotopes) are possible with the NanoSIMS.