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I Dillmann,
T Faestermann,
G Korschinek,
J Lachner, M Maiti,
M poutivtsev,
G Rugel,
S Walter,
F Kappeler,
M Erhard,
A R Junghans,
C Nair,
R Schwengner,
A Wagner,
M Pignatari,
T Rauscher,
A Mengoni
Proc. Intern.Symposium on Nuclei in the Cosmos XI; 01/2010
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I Dillmann,
T Faestermann,
G Korschinek,
J Lachner, M Maiti,
M Poutivtsev,
G Rugel,
S Walter,
F Kappeler,
M Erhard,
A R Junghans,
C Nair,
R Schwengner,
A Wagner
Nucl.Instrum.Methods Phys.Res. 01/2010; B268:1283.
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I Dillmann,
T Faestermann,
G Korschinek,
J Lachner, M Maiti,
M poutivtsev,
G Rugel,
S Walter,
F Kappeler,
M Erhard,
A R Junghans,
C Nair,
R Schwengner,
A Wagner,
M Pignatari,
T Rauscher,
A Mengoni
Proc. Intern.Symposium on Nuclei in the Cosmos XI; 01/2010
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I. Dillmann,
T. Faestermann,
G. Korschinek,
J. Lachner, M. Maiti,
M. Poutivtsev,
G Rugel,
S. Walter,
F. Käppeler,
M. Erhard,
A. R. Junghans,
C. Nair,
R. Schwengner,
A Wagner
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ABSTRACT: An accurate knowledge of the neutron capture cross sections of 62,63Ni is crucial since both isotopes take key positions which affect the whole reaction flow in the weak s process up to A=90. No experimental value for the 63Ni(n,gamma) cross section exists so far, and until recently the experimental values for 62Ni(n,gamma) at stellar temperatures (kT=30 keV) ranged between 12 and 37 mb. This latter discrepancy could now be solved by two activations with following AMS using the GAMS setup at the Munich tandem accelerator which are also in perfect agreement with a recent time-of-flight measurement. The resulting (preliminary) Maxwellian cross section at kT=30 keV was determined to be 30keV = 23.4 +/- 4.6 mb. Additionally, we have measured the 64Ni(gamma,n)63Ni cross section close to threshold. Photoactivations at 13.5 MeV, 11.4 MeV and 10.3 MeV were carried out with the ELBE accelerator at Forschungszentrum Dresden-Rossendorf. A first AMS measurement of the sample activated at 13.5 MeV revealed a cross section smaller by more than a factor of 2 compared to NON-SMOKER predictions. Comment: Proceedings of the 11th International Conference on Accelerator Mass Spectrometry in Rome, Sept. 14-19, 2008; to be published in Nucl. Instr. Meth. A
07/2009;
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C. Domingo‐Pardo,
I. Dillmann,
T. Faestermann,
U. Giesen,
J. Görres,
M. Heil,
S. Horn,
F. Käppeler,
S. Köchli,
G. Korschinek, [......],
J. Neuhausen,
R. Nolte,
M. Poutivtsev,
R. Reifarth,
R. Rugel,
D. Schumann,
E. Uberseder,
F. Voss,
S. Walter,
M. Wiescher
[show abstract]
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ABSTRACT: The s process synthesizes the elements between Fe and Sr in massive stars during two major evolutionary stages, convective core He burning and C shell burning. This scenario implies fascinating consequences for the chemical evolution of the star. For instance, the neutron capture rate at each isotope can have a big influence on the production of many of the subsequent higher mass isotopes. Correspondingly, one needs to know the (n,γ) cross sections of the involved isotopes with high accuracy in order to determine the abundance pattern reliably and to obtain a consistent picture of this stage. This contribution gives an overview on recent and future experiments for the Fe∕Ni nucleosynthesis in massive stars. New results on 60Fe, 62Ni and 64Ni are reported. 60Fe is mostly produced during the short convective C shell burning phase, where peak densities of ∼ 1011 cm−3 are reached, prior to the SN explosion. The stellar (n,γ) cross section of 60Fe could be measured with a 1 μg sample obtained at PSI (Switzerland), which was sufficient for an activation measurement using the intense, quasi‐stellar neutron field for a thermal energy of 25 keV at the Karlsruhe Van de Graaff accelerator. The FZK accelerator was also used for an activation of 62Ni, whereas in this case, the number of 63Ni nuclei produced were determined via accelerator mass spectroscopy at the Maier‐Leibnitz‐Laboratorium in Garching∕Munich. The (n,γ) cross section of 64Ni at a stellar temperature equivalent to 50 keV has been measured in a collaboration between FZK Karlsruhe and PTB Braunschweig. Finally, complementary time of flight measurements on the Fe and Ni isotopes over a broad energy range are planned at the white neutron source ṉTOF of CERN for the future campaign in 2009.
AIP Conference Proceedings. 01/2009; 1090(1):230-237.
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C Domingo-Pardo,
I Dillmann,
T Faestermann,
U Giesen,
J Gorres,
M Heil,
S Horn,
F Kappeler,
S Kochli,
G Korschinek, [......],
J Neuhausen,
R Nolte,
M Poutivtsev,
R Reifarth,
R Rugel,
D Schumann,
E Uberseder,
F Voss,
S Walter,
M Wiescher
Proc.13th Intern.Symposium on Capture Gamma-Ray Spectroscopy and Related Topics; 01/2009
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01/2008;
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01/2008;
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G. Korschinek,
A. Bergmaier,
T. Faestermann,
U.C. Gerstmann,
K. Knie,
G. Rugel,
A. Wallner,
I. Dillmann,
G. Dollinger,
Ch. Lierse von Gostomski,
K. Kossert, M. Maiti,
M. Poutivtsev,
A. Remmert
[show abstract]
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ABSTRACT: The importance of 10Be in different applications of accelerator mass spectrometry (AMS) is well-known. In this context the half-life of 10Be has a crucial impact, and an accurate and precise determination of the half-life is a prerequisite for many of the applications of 10Be in cosmic-ray and earth science research. Recently, the value of the 10Be half-life has been the centre of much debate. In order to overcome uncertainties inherent in previous determinations, we introduced a new method of high accuracy and precision. An aliquot of our highly enriched 10Be master solution was serially diluted with increasing well-known masses of 9Be. We then determined the initial 10Be concentration by least square fit to the series of measurements of the resultant 10Be/9Be ratio. In order to minimize uncertainties because of mass bias which plague other low-energy mass spectrometric methods, we used for the first time Heavy-Ion Elastic Recoil Detection (HI-ERD) for the determination of the 10Be/9Be isotopic ratios, a technique which does not suffer from difficult to control mass fractionation. The specific activity of the master solution was measured by means of accurate liquid scintillation counting (LSC). The resultant combination of the 10Be concentration and activity yields a 10Be half-life of T1/2 = 1.388 ± 0.018 (1 s, 1.30%) Ma. In a parallel but independent study (Chmeleff et al. [11]), found a value of 1.386 ± 0.016 (1.15%) Ma. Our recommended weighted mean and mean standard error for the new value for 10Be half-life based on these two independent measurements is 1.387 ± 0.012 (0.87%) Ma.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms.
