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CONSIDERATIONS FOR THE DEVELOPMENT OF THE UNIVERSITY OF ALBERTA COSMOGENIC ISOTOPE LABORATORY

DOUPé, JONATHAN P.  University of Alberta.
England , John H.  University of Alberta.
Litherland, A.E.  University of Toronto.
Zhao, X.-L.  University of Toronto.

The University of Alberta is developing a sample preparation laboratory for surface exposure dating with cosmogenic isotopes (Be-10, Al-26, and Cl-36). This talk will present some of the challenges encountered in the planning of this laboratory, and with surface exposure dating in general. Each phase of the procedure is critical to obtaining accurate measurements: sample selection, chemical preparation, Accelerator Mass Spectrometry (AMS) measurement, and data interpretation. Uncertainties in the production rates of cosmogenic nuclides, and the strength of the cosmic ray flux over time must be considered. Additionally, there are a number of analytical issues involved in this work. In the case of Be-10 analysis, the removal of meteoric Be-10 through acid etching is of critical importance for surface exposure dating. The use of hydrofluoric and perchloric acids during sample processing raises a number of laboratory design and safety issues. There have also been a number of new developments in Accelerator Mass Spectrometry (AMS) that should allow measurements on much smaller accelerators than previously thought possible. Work at the IsoTrace Laboratory of the University of Toronto has shown that Be-10 can be analyzed as the negative ion BeF- without interference from B-10 due to the instability of the ion BF-. Similarly, in the case of Cl-36, ion-molecule reactions at eV-energies have been shown to attenuate the isobar S-36. These developments promise to greatly expand the availability and application of cosmogenic isotope measurements in the future.


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