Improved particle location and isotopic screening measurements of sub-micron sized particles by Secondary Ion Mass Spectrometry

There are a number of applications within cosmochemistry, environmental studies, nuclear safeguards and nuclear forensic analyses that require capabilities for the location and isotopic measurement of sub-micron to micron-sized particles. This task can be divided into two sub-tasks: the first problem is to find the particle of interest in a matrix of other materials and the second is to perform accurate and precise isotopic measurements of the individual particles. This paper describes results obtained on real and standard samples using a newly developed Automated Particle Measurement (APM) software, for both Small Geometry (SG) and Large Geometry (LG) Secondary Ion Mass Spectrometry (SIMS) instruments. The speed and quality of screening measurements, in particular on the LG-SIMS, are far better than previously available. This paper mainly focuses on the analyses of uranium particles for safeguards verification purposes, but the described method can also be used for other applications.