Fluoride sample matrices and reaction cells — new capabilities for isotope measurements in accelerator mass spectrometry

¹ IsoTrace Laboratory and Department of Physics, University of Ottawa 150 Louis Pasteur, Ottawa K1N 6N5 Canada
² IsoTrace Laboratory, University of Toronto - 60 Saint George St. Toronto, M5S 1A7 Canada

Abstract

Two new techniques, which extend the range of elements that can be analyzed by Accelerator Mass Spectrometry (AMS), and which increase its isobar selection capabilities, have been recently introduced. The first consists of embedding the sample material in a fluoride matrix (e.g. PbF₂), which facilitates the production, in the ion source, of fluoride molecular anions that include the isotope of interest. In addition to forming anions with large electron binding energies and thereby increasing the range of analysable elements, in many cases by selection of a molecular form with a particular number of fluorine atoms, some isobar discrimination can be obtained. The second technique, for the significant reduction of atomic isobar interferences, is used following mass selection of the rare isotope. It consists of the deceleration, cooling and reaction of the rare mass beam with a gas, selected so that unwanted isobars are greatly attenuated in comparison with the isotope of interest. Proof of principle measurements for the analysis of ³⁶C1 and ⁴¹Ca have provided encouraging results and work is proceeding on the integration of these techniques in a new AMS system planned for installation in late 2012 at the University of Ottawa.