Secondary ion mass spectrometry is applied to a wide range of Geoscience applications because of its capability to provide direct in situ measurement of elemental and isotopic composition. The CAMECA IMS 1280 and 1280-HR are large geometry ultra-high sensitivity ion microprobes that provide excellent precision and reproducibility for isotope ratio measurements. A precision at the tenth permil level is routinely achieved for the measurement of 18 O/ 16 O ratio from 10 mm spots using multicollection Faraday Cups. However, analytical artifacts related to the surface topography and to the location of the analysis in the sample (X-Y effects) are known to bias the precision for isotope analysis. The X-Y effects have been investigated using a CAMECA prototype sample holder design. Results show a significant improvement in terms of reproducibility for analyses performed over a large area of the sample. Detailed analytical data using the new sample holder will be presented.

Secondary ion mass spectrometry (SIMS) is a powerful technique for in situ triple oxygen isotope measurements that has been used for more than 30 years. Since pioneering works performed on small-radius ion microprobes in the mid-80s, tremendous progress has been made in terms of analytical precision, spatial resolution and analysis duration. In this respect, the emergence in the mid-90s of the large-radius ion microprobe equipped with a multi-collector system (MC-SIMS) was a game changer. Further developments achieved on CAMECA MC-SIMS since then (e.g., stability of the electronics, enhanced transmission of secondary ions, automatic centering of the secondary ion beam, enhanced control of the magnetic field, 1012Ω resistor for the Faraday cup amplifiers) allow nowadays to routinely measure oxygen isotopic ratios (18O/16O and 17O/16O) in various matrices with a precision (internal error and reproducibility) better than 0.5‰ (2σ), a spatial resolution smaller than 10 µm and in a few minutes per analysis. This paper focuses on the application of the MC-SIMS technique to the in situ monitoring of mass-independent triple oxygen isotope variations.

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This paper describes and discusses how isotope measurements of low content uranium materials can be optimized using a multi-ion counting system consisting of five discrete dynode electron multiplier (EM) detectors.

Large geometry secondary ion mass spectrometry can be efficiently used to analyze uranium aerosol particles from dust samples in the search for undeclared nuclear activities. Automated sample screening measurements are followed by more precise and accurate microbeam measurements of both the major and minor uranium isotopes on selected individual particles. The quality of this work is essential in order to be able to draw valuable safeguards conclusions. This paper describes the latest developments that have been undertaken to enhance the detection limits and to reduce the uranium isotope measurement uncertainty. It includes improvements in the analytical protocol as well as in the instrument acquisition software and data reduction method. Recent useful yield measurements have been performed on uranium monodispersed particles using different primary bombardment conditions to compare to previously obtained data. Comparison of uranium isotope measurements when using pyrolytic graphite or silica planchets as a sample substrate will also be presented.