Düsseldorf 2007 – wissenschaftliches Programm
MS 3.4: Vortrag
Dienstag, 20. März 2007, 15:00–15:15, 5F
Cl-36 exposure dating with a 3-MV tandem — •Peter Steier1, Oliver Forstner1, Robin Golser1, Walter Kutschera1, Silke Merchel2, Tobias Orlowski1, Alfred Priller1, Christof Vockenhuber3, and Anton Wallner1 — 1VERA Laboratory, Faculty of Physics, Universität Wien, Vienna, Austria — 2Centre Européen de Recherche et d’Enseignement des Géosciences de l’Environnement (CEREGE), Aix En Provence, France — 3TRIUMF Laboratory, Vancouver, B.C., Canada
We have developed a method to detect 36Cl at natural isotopic concentrations with a 3-MV tandem AMS (Accelerator Mass Spectrometry) system. Several techniques were compared to distinguish 36Cl from (stable) 36S ions based on their different energy loss in matter. The best results were obtained by separating the ions in an optimized ionization chamber (developed at the ETH/PSI, Zürich, Switzerland) with a split anode providing, providing a relative suppression of 36S of 30000. This resulted in a measurement with a sulfur-induced background for 36Cl/Cl of 3x10−14. Further improvements are expected.
First measurements on exposure dating samples were performed for sites in Italy and Iran, already dated by other laboratories, in the 105 and 106 atoms Cl-36/g rock range, respectively. We observe a good general agreement, but a yet unexplained systematic offset of 25% of our results. These first measurements demonstrate that also 3-MV tandems, constituting the majority of dedicated AMS facilities, are capable of 36Cl exposure dating, which is presently the domain of larger facilities.