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8. Precise measurement of the thermal and stellar $^{54}$Fe($n, \gamma$)$^{55}$Fe cross sections via AMS

Author

Wallner, Anton, Belgya, Tamas, Buczak, Kathrin, Coquard, Laurent, Bichler, Max, Dillmann, Iris, Golser, Robin, Käppeler, Franz, Karakas, Amanda, Kutschera, Walter, Lederer, Claudia, Mengoni, Alberto, Pignatari, Marco, Priller, Alfred, Reifarth, Rene, Steier, Peter, and Szentmiklosi, Laszlo

Subjects
Nuclear Experiment, Astrophysics - Solar and Stellar Astrophysics
Abstract

The detection of long-lived radionuclides through ultra-sensitive single atom counting via accelerator mass spectrometry (AMS) offers opportunities for precise measurements of neutron capture cross sections, e.g. for nuclear astrophysics. The technique represents a truly complementary approach, completely independent of previous experimental methods. The potential of this technique is highlighted at the example of the $^{54}$Fe($n, \gamma$)$^{55}$Fe reaction. Following a series of irradiations with neutrons from cold and thermal to keV energies, the produced long-lived $^{55}$Fe nuclei ($t_{1/2}=2.744(9)$ yr) were analyzed at the Vienna Environmental Research Accelerator (VERA). A reproducibility of about 1% could be achieved for the detection of $^{55}$Fe, yielding cross section uncertainties of less than 3%. Thus, the new data can serve as anchor points to time-of-flight experiments. We report significantly improved neutron capture cross sections at thermal energy ($\sigma_{th}=2.30\pm0.07$ b) as well as for a quasi-Maxwellian spectrum of $kT=25$ keV ($\sigma=30.3\pm1.2$ mb) and for $E_n=481\pm53$ keV ($\sigma= 6.01\pm0.23$ mb). The new experimental cross sections have been used to deduce improved Maxwellian average cross sections in the temperature regime of the common $s$-process scenarios. The astrophysical impact is discussed using stellar models for low-mass AGB stars.

Published
2016
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9. The Link Between the Local Bubble and Radioisotopic Signatures on Earth

Author

Feige, Jenny, Breitschwerdt, Dieter, Wallner, Anton, Schulreich, Michael M., Kinoshita, Norikazu, Paul, Michael, Dettbarn, Christian, Fifield, L. Keith, Golser, Robin, Honda, Maki, Linnemann, Ulf, Matsuzaki, Hiroyuki, Merchel, Silke, Rugel, Georg, Steier, Peter, Tims, Stephen G., Winkler, Stephan R., and Yamagata, Takeyasu

Subjects
Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract

Traces of 2-3 Myr old 60Fe were recently discovered in a manganese crust and in lunar samples. We have found that this signal is extended in time and is present in globally distributed deep-sea archives. A second 6.5-8.7 Myr old signature was revealed in a manganese crust. The existence of the Local Bubble hints to a recent nearby supernova-activity starting 13 Myr ago. With analytical and numerical models generating the Local Bubble, we explain the younger 60Fe-signature and thus link the evolution of the solar neighborhood to terrestrial anomalies., Comment: 4 pages, 3 figures, accepted for publication in JPS Conf. Proc

Published
2016
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12. Radiocarbon ages of microcrystalline authigenic carbonate in Lake Neusiedl (Austria) suggest millennial‐scale growth of Mg‐calcite and protodolomite.

Author

Neuhuber, Stephanie, Gier, Susanne, Draganits, Erich, Steier, Peter, Bolka, Monika, Ottner, Franz, Spötl, Christoph, Hippler, Dorothee, and Meister, Patrick

Subjects
CALCITE, DOLOMITE, LAST Glacial Maximum, CARBON isotopes, CARBONATE minerals, LAKE sediments, LAKES
Abstract

Authigenic Mg‐calcite and dolomite are frequently observed in restricted, evaporative environments, such as lagoon or lake systems, but their formation is difficult to capture due to slow growth rates. Lake Neusiedl, an alkaline and subhaline lake with a mean water depth of 0.7 m in Austria, offers a natural system to study the precipitation of Ca‐Mg‐carbonate phases, which occur as fine‐grained, unconsolidated and largely homogenized mud. To elucidate the timing and formation mechanisms of these authigenic carbonate phases, the mineralogical and isotopic composition and radiocarbon age of different sediment grain‐size fractions from <0.2 to >3.0 μm were analysed. X‐ray diffraction analyses show two broad peaks of Mg‐calcite and protodolomite (lacking ordering peaks), suggesting that the carbonates are authigenic rather than detrital in origin. Calibrated carbon‐14 ages range between 200 cal yr bp and 3700 cal yr bp. The linear correlation of age and grain size suggests a very slow growth rate of single crystals of 0.23 to 0.60 μm/ka. These rates suggest an extremely slow sedimentation rate in a shallow lake that existed during most of the Holocene. The higher abundance of protodolomite in older grain fractions, in contrast to the presence of high‐Mg calcite in the youngest fractions, suggests a growth succession where high‐Mg calcite develops first and subsequently transforms into protodolomite. Much higher ages of 6 cal ka bp to 15 cal ka bp are measured in carbonates of lake deposits exposed on land, in a section north‐west of the recent lake, suggesting a growth rate of those carbonate minerals of 0.13 μm/ka. These time constraints further suggest that some carbonate grains could already have nucleated from lake water before or during the last glacial maximum, although under slightly different hydrochemical conditions. [ABSTRACT FROM AUTHOR]

Published
2024
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37. Deciphering sources of U contamination using isotope ratio signatures in the Loire River sediments: Exploring the relevance of 233U/236U and stable Pb isotope ratios

Author

Morereau, Amandine, primary, Jaegler, Hugo, additional, Hain, Karin, additional, Steier, Peter, additional, Golser, Robin, additional, Beaumais, Aurélien, additional, Lepage, Hugo, additional, Eyrolle, Frédérique, additional, Grosbois, Cécile, additional, Cazala, Charlotte, additional, and Gourgiotis, Alkiviadis, additional

Published
2022
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40. The quest for AMS of 182Hf – why poor gas gives pure beams

Author

Martschini Martin, Lachner Johannes, Merchel Silke, Priller Alfred, Steier Peter, Wallner Anton, Wieser Alexander, and Golser Robin

Subjects
Physics, QC1-999
Abstract

The long-lived radioisotope 182Hf (T1/2 = 8.9 Ma) is of high astrophysical interest as its potential abundance in environmental archives would provide insight into recent r-process nucleosynthesis in the vicinity of our solar system. Despite substantial efforts, it could not be measured at natural abundances with conventional AMS so far due to strong isobaric interference from stable 182W. Equally important is an increase in ion source efficiency for the anions of interest. The new Ion Laser InterAction Mass Spectrometry (ILIAMS) technique at VERA tackles the problem of elemental selectivity in AMS with a novel approach. It achieves near-complete suppression of isobar contaminants via selective laser photodetachment of decelerated anion beams in a gas-filled radio-frequency quadrupole (RFQ) ion cooler. The technique exploits differences in electron affinities (EA) within elemental or molecular isobaric systems neutralizing anions with EAs smaller than the photon energy. Alternatively, these differences in EA can also facilitate anion separation via chemical reactions with the buffer gas. We present first results with this approach on AMS-detection of 182Hf. With He +O2 mixtures as buffer gas in the RFQ, suppression of 182WF5− vs 180HfF 5− by >105 has been demonstrated. Mass analysis of the ejected anion beam identified the formation of oxyfluorides as an important reaction channel. The overall Hf-detection efficiency at VERA presently is 1.4% and the W-corrected blank value is 182Hf/180Hf = (3.4 ± 2.1)×10−14. In addition, a survey of different sample materials for highest negative ion yields of HfF 5− with Cs-sputtering has been conducted.

Published
2020
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41. The movements of Alpine glaciers throughout the last 10,000 years as sensitive proxies of temperature and climate changes

Author

Kutschera Walter, Patzelt Gernot, Schaefer Joerg M., Schlüchter Christian, Steier Peter, and Wild Eva Maria

Subjects
Physics, QC1-999
Abstract

A brief review of the movements of Alpine glaciers throughout the Holocene in the Northern Hemisphere (European Alps) and in the Southern Hemisphere (New Zealand Southern Alps) is presented. It is mainly based on glacier studies where 14C dating, dendrochronology and surface exposure dating with cosmogenic isotopes is used to establish the chronology of advances and retreats of glaciers. An attempt is made to draw some general conclusions on the temperature and climate differences between the Northern and Southern Hemisphere.

Published
2020
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42. Comparison and performance of two cosmogenic nuclide sample preparation procedures of in situ produced 10Be and 26Al

Author

Ruszkiczay-Rüdiger, Zsófia, Neuhuber, Stephanie, Braucher, Regis, Lachner, Johannes, Steier, Peter, Wieser, Alexander, Braun, Mihály, Bourlès, Didier, Aumaître, Georges, Keddadouche, Karim, Aster, Team, Research Centre for Astronomy and Earth Sciences [Budapest], Hungarian Academy of Sciences (MTA), University of Natural Resources and Life Sciences (BOKU), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Universität Wien, and Universität für Bodenkultur Wien = University of Natural Resources and Life [Vienne, Autriche] (BOKU)

Subjects
In situ, Materials science, Health, Toxicology and Mutagenesis, Sample processing, 010502 geochemistry & geophysics, 01 natural sciences, Analytical Chemistry, Fluoride precipitates, Al, chemistry.chemical_compound, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Radiology, Nuclear Medicine and imaging, Sample preparation, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Cosmogenic nuclide, Comparison of laboratory protocols, Spectroscopy, 0105 earth and related environmental sciences, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Radionuclide, Reproducibility, 010401 analytical chemistry, Radiochemistry, Extraction (chemistry), Public Health, Environmental and Occupational Health, Be, Pollution, 0104 chemical sciences, Nuclear Energy and Engineering, chemistry, Cosmogenic radionuclides, Fluoride
Abstract

Cosmogenic radionuclide 10Be and 26Al targets (BeO and Al2O3) for AMS analysis are produced by a growing number of geochemical laboratories, employing different sample processing methods for the extraction of Be and Al from environmental materials. The reliability of this geochronological tool depends on data reproducibility independent from the preparation steps and the AMS measurements. Our results demonstrate that 10Be and 26Al concentrations of targets processed following different, commonly used protocols and measured at two AMS facilities lead to consistent results. However, insoluble fluoride precipitates, if formed during processing, can cause decreased 26Al results, while 10Be concentrations are unaffected.

Published
2021

49. AMS of 36Cl with the VERA 3 MV tandem accelerator

Author

Martschini, Martin, Andersson, Pontus, Forstner, Oliver, Golser, Robin, Hanstorp, Dag, Lindahl, Anton O., Kutschera, Walter, Pavetich, Stefan, Priller, Alfred, Rohlén, Johan, Steier, Peter, Suter, Martin, and Wallner, Anton

Published
2013
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