ai-SIMS is a cornerstone technique, combining key capabilities of SIMS and AMS to improve composition microanalysis
ai-SIMS is a cornerstone technique, combining key capabilities of SIMS and AMS to improve composition microanalysis

A new type of Secondary Ion Mass Spectrometer (SIMS) is under development at the NRL that will quantitatively measure elements and isotopes at unprecedented low abundance levels. The new instrument combines a dynamic SIMS with a Single Stage Accelerator Mass Spectrometer (SSAMS). SIMS is known for its high spatial resolution and high sample utilization. The addition of a SSAMS, accepting ions in place of the usual ion detector of the SIMS instrument, enables destruction of molecular ions that often interfere with SIMS measurements of trace species; typical for elements heavier than Zr (approximately 90 u), enabling purely atomic ion SIMS (ai-SIMS) analysis. The single stage nature of this AMS allows detection of positive ions, not normally available to AMS measurements. Trace level sensitivity for actinide, lanthanide, many transition metal, alkali, and alkali-earth elements will be greatly improved while retaining SIMS capabilities for spatial and depth distribution analysis, and allowing micrometer-scale features to be characterized. This world-unique capability will be applied to:
  • Problems in nuclear safeguards and forensics
  • Analysis of trace impurities in new engineered materials and structures being developed for high power electronics and sensors
  • Measurement and location of contaminants in coatings and failed components
  • Elemental and isotopic compositional analysis of high-value materials, such as those from NASA spacecraft sample-return missions.
Dynamic SIMS is a proven tool, providing composition information at the micrometer scale. However, abundant molecular ions formed from ubiquitous surface species limit sensitivity for trace elements and isotopes.
Dynamic SIMS is a proven tool, providing composition information at the micrometer scale. However, abundant molecular ions formed from ubiquitous surface species limit sensitivity for trace elements and isotopes.
For masses above ~90 u, the mass resolution required to remove common molecular interferences exceeds the capability of SIMS for measuring trace species.
For masses above ~90 u, the mass resolution required to remove common molecular interferences exceeds the capability of SIMS for measuring trace species.
63Cu2 Molecule Destruction by ai-SIMS
Initial data from the NRL ai-SIMS demonstrates proof of concept. a) Ar breakup gas reduced 63Cu2 intensity by 107, enabling measurement of a likely trace level of 126Te, while b) only reducing 63Cu intensity by 70%.