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Now showing items 17 - 29 of 29

  • Editorial

    Kutschera, Walter   Golser, Robin   Priller, Alfred   Strohmaier, Brigitte  

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  • Applications of nuclear physics

    Kutschera, Walter  

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  • New Chronological Frame for the Young Neolithic Baden Culture in Central Europe (4th Millennium BC)

    Wild, Eva Maria   Stadler, Peter   Bondár, Mária   Draxler, Susanne   Friesinger, Herwig   Kutschera, Walter   Priller, Alfred   Rom, Werner   Ruttkay, Elisabeth   Steier, Peter  

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  • D-REAMS:A NEW COMPACT AMS SYSTEM FOR RADIOCARBON MEASUREMENTS AT THE WEIZMANN INSTITUTE OF SCIENCE,REHOVOT,ISRAEL

    Regev, Lior   Steier, Peter   Shachar, Yigal   Mintz, Eugenia   Wild, Eva Maria   Kutschera, Walter   Boaretto, Elisabetta  

    The Dangoor REsearch Accelerator Mass Spectrometer (D-REAMS) is a dedicated carbon-only AMS system, built by National Electrostatics Corporation (NEC). It is based on the 1.5SDH Pelletron, operating at 460 keV. The machine was installed at the Weizmann Institute of Science, Rehovot, Israel, in January-February 2013, and passed the acceptance test on March 2013. Since then, over 4500 samples have been successfully measured. Here, we present the results of an intercomparison experiment, done in collaboration with the Vienna Environmental Research Accelerator (VERA), and some typical operation parameters and measurement values of the new AMS system.
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  • Carbon background and ionization yield of an AMS system during C-14 measurements of microgram-size graphite samples

    Liebl, Jakob   Steier, Peter   Golser, Robin   Kutschera, Walter   Mair, Klaus   Priller, Alfred   Vonderhaid, Iris   Wild, Eva Maria  

    For C-14 AMS measurements of samples at the microgram level, ion source related effects start to play a role, while generally the lower sample size limit is set by the carbon background introduced during chemical preparation procedures. Measurements of about 800 graphite targets in the mass range of 1-100 mu g were performed within 25 AMS beam-times during the last three years at VERA, revealing a dependency of measured C-14(3+)/C-12(3+) ratios on C-12(3+) currents. This dependency can be accounted for by assuming a background current, which was determined for each AMS measurement by least square fitting. C-12(-) ion currents extracted from microgram graphite samples were typically (1.0 +/- 0.5) mu A / mu g C. On average a C-12(3+) background current of (0.14 +/- 0.14) mu A with (FC)-C-14 = 0.22 +/- 0.46 (skewness gamma(1) = 3.0) was deduced with significant variations between single measurements. The determination of this background current for each AMS measurement of microgram graphite samples allowed to apply a quantitative correction and thereby to improve the AMS measurement precision. Furthermore, the yield of graphitization and ionization in a Cs sputter ion source of graphitized microgram CO2 samples was investigated. No dependency on the cathode target geometry was observed for 9 differently shaped cathode types. (C) 2012 Elsevier B.V. All rights reserved.
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  • Accelerator mass spectrometry: Counting atoms rather than decays

    Kutschera, Walter  

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  • Cosmogenic (26)Al in the atmosphere and the prospect of a (26)Al/(10)Be chronometer to date old ice RID G-1480-2011

    Auer, Matthias   Wagenbach, Dietmar   Wild, Eva Maria   Wallner, Anton   Priller, Alfred   Miller, Heinrich   Schlosser, Clemens   Kutschera, Walter  

    Cosmogenic radionuclides in the one-million-year half-life range offer unique possibilities for age determinations in geophysics. In measurements where the radioactive decay is being utilized as a clock, uncertainties in age determinations may be reduced if the ratio of two radioisotopes with different half-lives can be used as a chronometer. In this work we investigate the atomic ratio of atmospheric (26)Al (t(1/2) = 0.717 Ma) to (10)Be (t(1/2) = 1.386 Ma) measured with accelerator mass spectrometry (AMS), and its potential as a chronometer for dating old ice. The (26)Al/(10)Be ratio decreases with an effective half-life of t(1/2)((26)Al/(10)Be) = 1.49 Ma. For its application as a chronometer, the atmospheric (26)Al/(10)Be ratio has to be well characterized. However, the properties of atmospheric (26)Al have been understood only poorly so far. At the VERA AMS facility of the University of Vienna, a first systematic study of the global variations of the (26)Al/(10)Be ratio in the atmosphere and in surface firn has been carried out, and pilot measurements of the (26)Al/(10)Be ratio in deep Antarctic ice have been performed. Our results indicate that this ratio is globally constant to within 5% in the atmosphere and in surface firn with a mean value of 1.89 x 10(-3). The data also suggest that non-atmospheric sources of (26)Al, such as extraterrestrial, in situ produced or re-suspended (26)Al do not contribute significantly to the observed (26)Al/(10)Be ratio. in addition, atmospheric mixing seems to exert only a minor influence. In a first application of the method, (26)Al/(10)Be ratios were measured in chips collected in connection with the drilling of the lowest part of an ice core (2250 to 2760 m) in Dronning Maud Land, Antarctica. Surprisingly, variable (26)Al/(10)Be ratios ranging between 0.5 and up to 2 times the atmospheric ratio were found at different locations in this deep ice core. While the cause for the ratios higher than atmospheric remains unexplained so far, the ratios lower than atmospheric may be caused by radioactive decay, allowing a first dating attempt using the (26)Al/(10)Be ratio. Thus, at an ice depth of 2760 m an approximate date of (6.7 +/- 2.6) x 10(5) years was established. (C) 2009 Elsevier B.V. All rights reserved.
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  • Accelerator Mass Spectrometry: From Nuclear Physics to Dating

    Kutschera, Walter  

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  • von Kutschera Franz. Gottlob Frege. Eine Einführung in sein Werk. Walter de Gruyter, Berlin and New York 1989, x + 207 pp.

    Schirn   Matthias  

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  • F. von Kutschera: Platons Parmenides (de Gruyter Studienbuch). Pp. xi + 171. Berlin and New York: Walter de Gruyter, 1995. DM 88 (Paper, DM 48). ISBN: 3-11-01491-9 (3-11-014557-X pbk).

    Schofield, Malcolm  

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  • [AIP The 7th international symposium: Resonance ionization spectroscopy 1994 - Bernkastel-Kues, Germany (3−8 Jul 1994)] AIP Conference Proceedings - Atom counting with accelerator mass spectrometry

    Kutschera, Walter  

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  • Exotic negative molecules in AMS RID G-1480-2011

    Golser, Robin   Gnaser, Hubert   Kutschera, Walter   Priller, Alfred   Steier, Peter   Wallner, Anton  

    "The techniques and equipment developed for AMS studies are well suited for identifying exotic negative ions". With this sentence begins a pioneering paper by Roy Middleton and Jeff Klein (M&K) on small doubly-charged negative carbon clusters [Nucl. Instr. and Meth. B 123 (1997) 532]. M&K were the first to utilize Accelerator Mass Spectrometry to prove the existence of these clusters and a number of other exotic molecules. We review M&K's efforts and show how their work is being continued at other laboratories. The latest developments are: (1) the discovery of long-lived molecular hydrogen anions H-2(-), D-2(-) and (2) the unambiguous identification of the smallest doubly-charged negative molecule (LiF3)(2-). In particular we show new experimental data for D-3(-), and for (LiF3)(2-), and we try to answer the question why M&K's search for this di-anion was unsuccessful. (c) 2007 Flsevier B.V. All rights reserved.
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  • Developments toward the measurement of I-129 in lignite

    Wallner, Gabriele   Steier, Peter   Brandl, Thomas   Friesacher, Maria E.   Hille, Peter   Kutschera, Walter   Tatzber, Michael   Ayromlou, Shahram  

    The concentration of the long-lived radioisotope (129)I was determined in two Austrian lignite samples through (111)I/(127)I isotopic ratio measurement by AMS, and through a measurement of the total iodine content with an ion-selective electrode. In addition, the uranium concentration of the samples was measured by alpha-spectrometry. From the mean values of the uranium concentrations the steady-state of concentration in lignite was calculated; the concentrations derived from the measured (129)I/(127)I ratio and the total iodine con tent, however.. were much higher than expected.. clearly indicating that lignite does not represent a closed system for (129)I. The observed high ratio in the sample from the surface mine suggests the presence of anthropogenic (129)I, while the source for the high (129)I concentrations in the subsurface lignite is the addition of fissiogenic (129)I either from the lignite itself (from layers with much higher U content than in the samples investigated) or from nearby geological formations rich in uranium. (c) 2007 Elsevier B.V. All rights reserved.
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