TY - JOUR
T1 - 36Cl exposure dating with a 3-MV tandem
AU - Steier, Peter
AU - Forstner, Oliver
AU - Golser, Robin
AU - Kutschera, Walter
AU - Martschini, Martin
AU - Merchel, Silke
AU - Orlowski, Tobias
AU - Priller, Alfred
AU - Vockenhuber, Christof
AU - Wallner, Anton
PY - 2010/4
Y1 - 2010/4
N2 - 36Cl AMS measurements at natural isotopic concentrations have yet been performed only at tandem accelerators with 5 MV terminal voltage or beyond. We have developed a method to detect 36Cl at natural terrestrial isotopic concentrations with a 3-MV system, operated above specifications at 3.5 MV. An effective separation was obtained with an optimized split-anode ionization chamber design (adopted from the ETH/PSI Zurich AMS group), providing a suppression factor of up to 30,000 for the interfering isobar 36S. Despite the good separation, a relatively high sulfur output from the ion source (36S-/35Cl- ≈ 4 × 10-10 for samples prepared from chemically pure reagents), and a possibly cross contamination resulted in a background corresponding to 36Cl/Cl ≈ 3 × 10-14. The method was applied to samples containing between 105 and 106 atoms 36Cl/g rock from sites in Italy and Iran, which were already investigated by other laboratories for surface exposure dating. The 36Cl/Cl ratios in the range from 2 × 10-13 to 5 × 10-12 show a generally good agreement with the previous 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.
AB - 36Cl AMS measurements at natural isotopic concentrations have yet been performed only at tandem accelerators with 5 MV terminal voltage or beyond. We have developed a method to detect 36Cl at natural terrestrial isotopic concentrations with a 3-MV system, operated above specifications at 3.5 MV. An effective separation was obtained with an optimized split-anode ionization chamber design (adopted from the ETH/PSI Zurich AMS group), providing a suppression factor of up to 30,000 for the interfering isobar 36S. Despite the good separation, a relatively high sulfur output from the ion source (36S-/35Cl- ≈ 4 × 10-10 for samples prepared from chemically pure reagents), and a possibly cross contamination resulted in a background corresponding to 36Cl/Cl ≈ 3 × 10-14. The method was applied to samples containing between 105 and 106 atoms 36Cl/g rock from sites in Italy and Iran, which were already investigated by other laboratories for surface exposure dating. The 36Cl/Cl ratios in the range from 2 × 10-13 to 5 × 10-12 show a generally good agreement with the previous 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.
KW - AMS
KW - Cl
KW - Isobar separation
UR - http://www.scopus.com/inward/record.url?scp=77949908189&partnerID=8YFLogxK
U2 - 10.1016/j.nimb.2009.10.020
DO - 10.1016/j.nimb.2009.10.020
M3 - Article
SN - 0168-583X
VL - 268
SP - 744
EP - 747
JO - Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
JF - Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
IS - 7-8
ER -