Universität zu Köln

Schiffer, Markus, Stolz, Alexander, Lopez, Damian Alejandro, Spanier, Richard, Herb, Susan, Mueller-Gatermann, Claus, Heinze, Stefan, Binnie, Steven, Melchert, Jan, Kivel, Niko, Schumann, Dorothea, Rethemeyer, Janet, Dunai, Tibor and Dewald, Alfred (2020). Method developments for accelerator mass spectrometry at CologneAMS, Mn-53/He-3 burial dating and ultra-small (CO2)-C-14 samples. Glob. Planet. Change, 184. AMSTERDAM: ELSEVIER. ISSN 1872-6364

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Abstract

Accelerator mass spectrometry (AMS) has a great potential for various geological applications. The precision and sensitivity is directly linked to technical developments. Therefore CologneAMS, the center for accelerator mass spectrometry of the University of Cologne (Dewald et al., 2013a, 2013b), does extensive work on method developments for isotopic ratio measurement, for new applications and to improve the precision. We present two important technical developments: (1) dating of sediments with Mn-53 and (2) ultra-small (CO2)-C-14 samples. (1) The age determination of discontinuously deposited sediments by measurement of cosmogenic Mn-53 and He-3 concentration in iron-titaniumoxides (hematite, magnetite, titanomagnetite, ilmenite), where the measurement of the medium mass isotope Mn-53 is difficult because of the interfering isobar Cr-53. It can be measured at only 2 laboratories worldwide. The new AMS system at the Cologne 10 MV FN tandem accelerator is therefore designed especially for the measurement of medium mass isotopes, e.g. Mn-53. It provides the opportunity to use several detector systems in different combinations: degrader foils with an electrostatic analyzer, a 4 m time-of-flight system, a new 135 degrees gas-filled magnet, different gas ionization detectors and a projectile x-ray detector. With the implementation of the new 135 degrees gas-filled magnet to the 10 MV FN-Tandem accelerator AMS beamline the first tests have shown an increase in transmission and reduction of blank value in comparrison to the measurement with the degrader foil technique (Schiffer et al. 2018). The background level was reduced by a factor of 3.3 and the error normalized sensitivity (Schiffer et al. 2018) was increased by a factor of 1.6. (2) For the measurement of extremely low carbon from cosmogenic in-situ produced C-14 or from C-14 content of bulk sediments, with 0.01% carbon, technical developments are required to measure low concentrations in terrestrial rocks of 100,000 atoms g(-1) in quartz and to trace organic compounds with 10-50 mu g of (CO2)-C-14 samples. It turned out, that the measurement of (CO2)-C-14 micro-samples with the gas-ion source of the Cologne 6 MV AMS system in combination with a gas-handling system is an alternative to the development of a micro-scale graphitization. Modern 1 mu g CO2 samples,-)(C-14/C-12)= 1.18 x 10(-12) can be measured with this system with a precision of 2.8%. The overall efficiency is 4%-6% and the reproducibility of standard samples is 0.9% with a blank level of 3-6 x 10(-15).

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Schiffer, Markus UNSPECIFIED UNSPECIFIED UNSPECIFIED Stolz, Alexander UNSPECIFIED UNSPECIFIED UNSPECIFIED Lopez, Damian Alejandro UNSPECIFIED UNSPECIFIED UNSPECIFIED Spanier, Richard UNSPECIFIED UNSPECIFIED UNSPECIFIED Herb, Susan UNSPECIFIED UNSPECIFIED UNSPECIFIED Mueller-Gatermann, Claus UNSPECIFIED UNSPECIFIED UNSPECIFIED Heinze, Stefan UNSPECIFIED UNSPECIFIED UNSPECIFIED Binnie, Steven UNSPECIFIED UNSPECIFIED UNSPECIFIED Melchert, Jan UNSPECIFIED UNSPECIFIED UNSPECIFIED Kivel, Niko UNSPECIFIED UNSPECIFIED UNSPECIFIED Schumann, Dorothea UNSPECIFIED UNSPECIFIED UNSPECIFIED Rethemeyer, Janet UNSPECIFIED UNSPECIFIED UNSPECIFIED Dunai, Tibor UNSPECIFIED UNSPECIFIED UNSPECIFIED Dewald, Alfred UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-351978
DOI:	10.1016/j.gloplacha.2019.103053
Journal or Publication Title:	Glob. Planet. Change
Volume:	184
Date:	2020
Publisher:	ELSEVIER
Place of Publication:	AMSTERDAM
ISSN:	1872-6364
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute for Nuclear Physics
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language IN-SITU C-14; DEDICATED AMS SETUP; COSMOGENIC HE-3; EXTRACTION; UNIVERSITY; RATES; PROGRESS; MAGNET; SYSTEM; QUARTZ Multiple languages Geography, Physical; Geosciences, Multidisciplinary Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/35197