Ionisation efficiency improvements for AMS measurement of actinides

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Measurements of the isotopic ratios of plutonium and uranium are utilised by the safeguards community, environmental radioactivity and remediation studies, oceanography research, and in the U-series dating of geological samples. Accelerator Mass Spectrometry offers the advantages of high selectivity and sensitivity for such ratio measurements, but suffers from a poorer ionisation and transmission efficiency than some other mass spectrometric techniques. In addition, the ionisation efficiency achieved in caesium-sputter ion sources can be variable depending on the chemical form and geometry of the target used, yielding actinide negative ion beam rates with efficiencies ranging from 0.05% to 0.5%. In this paper we investigate the impact of the crystal structure of the target material, chemical composition and the geometry of the target in order to determine conditions which will allow us to maximise beam output and increase the efficiency of AMS measurements in future. We also examine target stability and “burn in time” (the time taken to generate a stable beam current) in conjunction with these measurements in order to maintain a high precision of measurement during the measurement period. © 2009 Published by Elsevier B.V.
Physical copy held by ANSTO Library at DDC 539.7.56
Plutonium, Uranium, Mass spectroscopy, Sputtering, Efficiency, Ionization
Child, D. P., Hotchkis, M. A. C., Whittle, K., & Zorko, B. (2010). Ionisation efficiency improvements for AMS measurement of actinides. Paper presented to the 11th International Conference on Accelerator Mass Spectrometry (AMS-11), 14th – 19th September 2008. Spazio Etoile, Rome. In Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 268(7-8), 820-823. doi:10.1016/j.nimb.2009.10.039