495 research outputs found

    KADoNiS-pp: The astrophysical pp-process database

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    The KADoNiS-pp project is an online database for cross sections relevant to the pp-process. All existing experimental data was collected and reviewed. With this contribution a user-friendly database using the KADoNiS (Karlsruhe Astrophysical Database of Nucleosynthesis in Stars) framework is launched, including all available experimental data from (p,╬│\gamma), (p,n), (p,╬▒\alpha), (╬▒\alpha,╬│\gamma), (╬▒\alpha,n) and (╬▒\alpha,p) reactions in or close to the respective Gamow window with cut-off date of August 2012 (www.kadonis.org/pprocess).Comment: Proceedings Nuclear Data Conference 2013, published in Nuclear Data Sheets 120 (2014) 19

    Neutron activation of natural zinc samples at kT = 25 keV

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    The neutron-capture cross sections of 64Zn, 68Zn, and 70Zn have been measured with the activation technique in a quasistellar neutron spectrum corresponding to a thermal energy of kT = 25 keV. By a series of repeated irradiations with different experimental conditions, an uncertainty of 3% could be achieved for the 64Zn(n,g)65Zn cross section and for the partial cross section 68Zn(n,g)69Zn-m feeding the isomeric state in 69Zn. For the partial cross sections 70Zn(n,g)71Zn-m and 70Zn(n,g)71Zn-g, which had not been measured so far, uncertainties of only 16% and 6% could be reached because of limited counting statistics and decay intensities. Compared to previous measurements on 64,68Zn, the uncertainties could be significantly improved, while the 70Zn cross section was found to be two times smaller than existing model calculations. From these results Maxwellian average cross sections were determined between 5 and 100 keV. Additionally, the beta-decay half-life of 71Zn-m could be determined with significantly improved accuracy. The consequences of these data have been studied by network calculations for convective core He burning and convective shell C burning in massive stars

    Stellar neutron capture cross sections of Ôü┤┬╣K and Ôü┤ÔüÁSc

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    The neutron capture cross sections of light nuclei (

    New Stellar (n,╬│)(n,\gamma) Cross Sections and The "Karlsruhe Astrophysical Database of Nucleosynthesis in Stars"

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    Since April 2005 a regularly updated stellar neutron cross section compilation is available online at http://nuclear-astrophysics.fzk.de/kadonis. This online-database is called the "Karlsruhe Astrophysical Database of Nucleosynthesis in Stars" project and is based on the previous Bao et al. compilation from the year 2000. The present version \textsc{KADoNiS} v0.2 (January 2007) includes recommended cross sections for 280 isotopes between 1^{1}H and 210^{210}Po and 75 semi-empirical estimates for isotopes without experimental information. Concerning stellar (n,╬│)(n,\gamma) cross sections of the 32 stable, proton-rich isotopes produced by the pp process experimental information is only available for 20 isotopes, but 9 of them have rather large uncertainties of Ôëą\geq9%. The first part of a systematic study of stellar (n,╬│)(n,\gamma) cross sections of the pp-process isotopes 74^{74}Se, 84^{84}Sr, 102^{102}Pd, 120^{120}Te, 130^{130}Ba, 132^{132}Ba, 156^{156}Dy, and 174^{174}Hf is presented. In another application \textsc{KADoNiS} v0.2 was used for an modification of a reaction library of Basel university. With this modified library pp-process network calculations were carried out and compared to previous results.Comment: Proceedings "International Conference on Nuclear Data for Science and Technology 2007", Nice/ Franc

    Stellar neutron capture cross sections of ┬▓Ôü░ ┬▓┬╣ ┬▓┬▓Ne

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    The stellar (n,╬│) cross sections of the Ne isotopes are important for a number of astrophysical quests, i.e., for the interpretation of abundance patterns in presolar material or with respect to the s-process neutron balance in red giant stars. This paper presents resonance studies of experimental data in the keV range, which had not been fully analyzed before. The analyses were carried out with the R-matrix code sammy. With these results for the resonant part and by adding the components due to direct radiative capture, improved Maxwellian-averaged cross sections (MACS) could be determined. At kT=30keV thermal energy we obtain MACS values of 240┬▒29,1263┬▒160, and 53.2┬▒2.7 ╬╝barn for ┬▓Ôü░Ne,┬▓┬╣Ne, and ┬▓┬▓Ne, respectively. In earlier work the stellar rates of ┬▓Ôü░Ne and ┬▓┬╣Ne had been grossly overestimated. ┬▓┬▓Ne and ┬▓Ôü░Ne are significant neutron poisons for the s process in stars because their very small MACS values are compensated by their large abundances

    Present status of the KADoNiS database

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    Opportunities for Nuclear Astrophysics at FRANZ

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    The "Frankfurter Neutronenquelle am Stern-Gerlach-Zentrum" (FRANZ), which is currently under development, will be the strongest neutron source in the astrophysically interesting energy region in the world. It will be about three orders of magnitude more intense than the well-established neutron source at the Research Center Karlsruhe (FZK)
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