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.
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
The normal incidence electron gun of the IMS4f is unique in design, allowing self-compensation of electric charges when negative secondary ions are analysed. Tbis is made possible owing to the formation of a cloud containing an excess of very-low-energy electroms above the sample surface. When positive charges appear at the sample surface, the sample will take out of the cloud the exact amount of electrons required for compensation. The effectiveness of this self-compensation is demonstrated by the analysis of bulk insulators, such as alumina and silicon nitride, as well as multihyered specimens.In the positive mode, exact adjustment of the electron intensity monitored by the energy distribution of secondary ions allows one to reach a state where the electric field inside the sample is small enough to make it possible to analyse very mobile elements, such as Li and Na, without migration. Misadjustment of the electron intensity will create an electric field at the surface and an equilibrium is observed owing to conduction currents.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.