No abstract

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.

A primary tool for detecting undeclared nuclear activities is the analysis of uranium-bearing particles collected on cotton swipes. For many years, secondary ion mass spectrometry (SIMS) has been used as one of the mainstay techniques for particle analysis of nuclear safeguards samples. SIMS is unique in that it is the only technique that can both localize the particles of interest and also provide the isotopic composition of single particles. This paper presents data obtained on standard uranium particle samples using large geometry (LG)-SIMS instruments equipped with the newly developed, automated particle measurement screening software. Both sample screening measurements and microbeam analyses on individual particles are presented. The enhanced performance of the SIMS method for nuclear safeguards applications using LG-SIMS instruments equipped with automated screening capabilities is also discussed. Figure 7. Microbeam measurements, (a) 234 U versus 235 U and (b) 236 U versus 235 U on particles selected from the screening measurement. Intersection of dotted lines indicates the nominal values for 234 U, 235 U, or 236 U atom % for SRM U005a and U010. Error bars correspond to AE 2s.Nuclear safeguards applications using LG-SIMS

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.