3,294 research outputs found
The Karlsruhe Astrophysical Database of Nucleosynthesis in Stars Project - Status and Prospects
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
Neutron-induced astrophysical reaction rates for translead nuclei
Neutron-induced reaction rates, including fission, are calculated in the
temperature range 1.d8 <T (K) < 1.d10 within the framework of the statistical
model for targets with atomic number 83 < Z < 119 (from Po to Uuo) from the
neutron to the proton drip-line. Four sets of rates have been calculated,
utilizing - where possible - consistent nuclear data for neutron separation
energies and fission barriers from Thomas-Fermi (TF), Extended Thomas-Fermi
plus Strutinsky Integral (ETFSI), Finite-Range Droplet Model (FRDM) and
Hartree-Fock-Bogolyubov (HFB) predictions. Tables of calculated values as well
as analytic seven parameter fits in the standard REACLIB format are supplied.
We also discuss the sensitivity of the rates to the input, aiming at a better
understanding of the uncertainties introduced by the nuclear input.Comment: 14 pages, 10 figures, 2 tables in paper, 2 in Annex and online tables
example
New Stellar Cross Sections and The "Karlsruhe Astrophysical Database of Nucleosynthesis in Stars"
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
H and Po and 75 semi-empirical estimates for isotopes without
experimental information. Concerning stellar cross sections of the
32 stable, proton-rich isotopes produced by the process experimental
information is only available for 20 isotopes, but 9 of them have rather large
uncertainties of 9%. The first part of a systematic study of stellar
cross sections of the -process isotopes Se, Sr,
Pd, Te, Ba, Ba, Dy, and 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 -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
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
-Process simulations with a modified reaction library
We have performed -process simulations with the most recent stellar
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 (`` 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 =126 shell closure.Comment: 5 pages, 1 figure Proceedings "Nuclear Physics in Astrophysics
NPA-III", Dresden/Germany (2007
R-process nucleosynthesis calculations with complete nuclear physics input
The r-process constitutes one of the major challenges in nuclear
astrophysics. Its astrophysical site has not yet been identified but there is
observational evidence suggesting that at least two possible sites should
contribute to the solar system abundance of r-process elements and that the
r-process responsible for the production of elements heavier than Z=56 operates
quite robustly producing always the same relative abundances. From the
nuclear-physics point of view the r-process requires the knowledge of a large
number of reaction rates involving exotic nuclei. These include neutron capture
rates, beta-decays and fission rates, the latter for the heavier nuclei
produced in the r-process. We have developed for the first time a complete
database of reaction rates that in addition to neutron-capture rates and
beta-decay half-lives includes all possible reactions that can induce fission
(neutron-capture, beta-decay and spontaneous fission) and the corresponding
fission yields. In addition, we have implemented these reaction rates in a
fully implicit reaction network. We have performed r-process calculations for
the neutrino-driven wind scenario to explore whether or not fission can
contribute to provide a robust r-process pattern
Solving the stellar 62Ni problem with AMS
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.
- âŠ