563 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,γ\gamma), (p,n), (p,α\alpha), (α\alpha,γ\gamma), (α\alpha,n) and (α\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

    pp-Process simulations with a modified reaction library

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    We have performed pp-process simulations with the most recent stellar (n,γ)(n,\gamma) cross sections from the "Karlsruhe Astrophysical Database of Nucleosynthesis in Stars" project (version v0.2, http://nuclear-astrophysics.fzk.de/kadonis). The simulations were carried out with a parametrized supernova type II shock front model (``γ\gamma process'') of a 25 solar mass star and compared to recently published results. A decrease in the normalized overproduction factor could be attributed to lower cross sections of a significant fraction of seed nuclei located in the Bi and Pb region around the NN=126 shell closure.Comment: 5 pages, 1 figure Proceedings "Nuclear Physics in Astrophysics NPA-III", Dresden/Germany (2007

    New Stellar (n,γ)(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,γ)(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 \geq9%. The first part of a systematic study of stellar (n,γ)(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 (n,gamma) cross sections of p-process isotopes PartI: 102Pd, 120Te, 130,132Ba,and 156Dy

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    We have investigated the (n,gamma) cross sections of p-process isotopes with the activation technique. The measurements were carried out at the Karlsruhe Van de Graaff accelerator using the 7Li(p,n)7Be source for simulating a Maxwellian neutron distribution of kT = 25 keV. Stellar cross section measurements are reported for the light p-process isotopes 102Pd, 120Te, 130,132Ba, and 156Dy. In a following paper the cross sections of 168Yb, 180W, 184Os, 190Pt, and 196Hg will be discussed. The data are extrapolated to p-process energies by including information from evaluated nuclear data libraries. The results are compared to standard Hauser-Feshbach models frequently used in astrophysics.Comment: 13 pages, 4 figure

    The Karlsruhe Astrophysical Database of Nucleosynthesis in Stars Project - Status and Prospects

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    The KADoNiS (Karlsruhe Astrophysical Database of Nucleosynthesis in Stars) project is an astrophysical online database for cross sections relevant for nucleosynthesis in the s process and the γ process. The s-process database (http://www.kadonis.org) was started in 2005 and is presently facing its 4th update (KADoNiS v1.0). The γ-process database (KADoNiS-p, http://www.kadonis.org/pprocess) was recently revised and re-launched in March 2013. Both databases are compilations for experimental cross sections with relevance to heavy ion nucleosynthesis. For the s process recommended Maxwellian averaged cross sections for kT=5-100 keV are given for more than 360 isotopes between 1H and 210Bi. For the γ-process database all available experimental data from (p, γ), (p, n), (p, α), (α, γ), (α, n), and (α, p) reactions between 70Ge and 209Bi in or close to the respective Gamow window were collected and can be compared to theoretical predictions. The aim of both databases is a quick and user-friendly access to the available data in the astrophysically relevant energy regions. © 2014 Elsevier Inc.Peer reviewe

    Adsorption and Reaction of Ethene on Cr2O3(0001)/Cr(110)

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    (n,γ) cross-sections of light p nuclei: Towards an updated database for the p process

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    Abstract.: The nucleosynthesis of elements beyond iron is dominated by the s and r processes. However, a small amount of stable isotopes on the proton-rich side cannot be made by neutron capture and is thought to be produced by photodisintegration reactions on existing seed nuclei in the so-called "p process”. So far most of the p-process reactions are not yet accessible by experimental techniques and have to be inferred from statistical Hauser-Feshbach model calculations. The parametrization of these models has to be constrained by measurements on stable proton-rich nuclei. A series of (n,γ) activation measurements on p nuclei, related by detailed balance to the respective photodisintegrations, was carried out at the Karlsruhe Van de Graaff accelerator using the 7Li(p, n) 7Be source for simulating a Maxwellian neutron distribution of kT = 25keV. We present here preliminary results of our extended measuring program in the mass range between A = 74 and A = 132, including first experimental (n,γ) cross-sections of 74Se, 84Sr, 120Te and 132Ba, and an improved value for 130Ba. In all cases we find perfect agreement with the recommended MACS predictions from the Bao et al. compilatio

    Maxwellian Neutron Spectrum generation and Stellar Cross-Section measurements: measurement of the 197Au(n,γ) MACS

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    Maxwellian-averaged cross-sections (MACS) are needed as an input for the models of stellar s- and r-processes nucleosynthesis. MACS can be obtained from activation measurements, irradiating a sample with the neutron field generated by the 7Li(p,n)7Be reaction at 1912 keV proton energy. At this energy, the neutron energy spectrum is close (R2≤0.9) to a Maxwellian one of kT=25 keV. However, it was shown that shaping the energy of the incident proton beam is possible to generate a neutron field with an energy spectrum much closer to a real Maxwellian (R2>0.995), therefore avoiding or minimizing corrections in the MACS calculation. We show a preliminary result of an experiment performed at JRC-IRMM (Geel) to confirm our method. We have measured the MACS30 (kT=30 keV) of the 197Au(n,γ) reaction, at CNA (Seville). We obtained 612 mb, in good agreement with the latest measurements
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