128 research outputs found
Nucleosynthesis simulations for the production of the p-nuclei 92Mo and 94Mo in a Supernova type II model
We present a nucleosynthesis sensitivity study for the Îł-process in a Supernova type II model within the NuGrid research platform. The simulations aimed at identifying the relevant local production and destruction rates for the p-nuclei of molybdenum and at determining the sensitivity of the final abundances to these rates. We show that local destruction rates strongly determine the abundance of 92 Mo and 94 Mo, and quantify the impact
Measurements of neutron-induced reactions in inverse kinematics and applications to nuclear astrophysics
Neutron capture cross sections of unstable isotopes are important for
neutron-induced nucleosynthesis as well as for technological applications. A
combination of a radioactive beam facility, an ion storage ring and a high flux
reactor would allow a direct measurement of neutron induced reactions over a
wide energy range on isotopes with half lives down to minutes. The idea is to
measure neutron-induced reactions on radioactive ions in inverse kinematics.
This means, the radioactive ions will pass through a neutron target. In order
to efficiently use the rare nuclides as well as to enhance the luminosity, the
exotic nuclides can be stored in an ion storage ring. The neutron target can be
the core of a research reactor, where one of the central fuel elements is
replaced by the evacuated beam pipe of the storage ring. Using particle
detectors and Schottky spectroscopy, most of the important neutron-induced
reactions, such as (n,), (n,p), (n,), (n,2n), or (n,f), could
be investigated.Comment: 5 pages, 7 figures, Invited Talk given at the Fifteenth International
Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS15),
Dresden, Germany, 201
Neutron-capture measurement candidates for the r-process in neutron star mergers
Neutron star mergers (NSMs) are one of the astrophysical sites for the occurrence of the rapid neutron capture process (r-process). After a merger, the ejected neutron-rich matter hosts the production of radioactive heavy nuclei located far from the stability valley. Their nuclear physics properties are key inputs for r-process nucleosynthesis calculations. Here, we focus on the importance of neutron-capture rates and perform a sensitivity study for typical outflows from NSMs. We identify the rates with the highest impact on the final r-process abundance pattern and the nuclear energy release, therefore determining the nucleosynthesis in NSMs. A list of major n-capture rates affecting individual isotopes and elements production is also provided
Experimental neutron capture data of 58Ni from the CERN n_TOF facility
CGS15 – Capture Gamma-Ray Spectroscopy and Related TopicsThe neutron capture cross section of 58Ni was measured at the neutron time of flight facility n_TOF at CERN, from 27 meV to 400 keV neutron energy. Special care has been taken to identify all the possible sources of background, with the so-called neutron background obtained for the first time using high-precision GEANT4 simulations. The energy range up to 122 keV was treated as the resolved resonance region, where 51 resonances were identified and analyzed by a multilevel R-matrix code SAMMY. Above 122 keV the code SESH was used in analyzing the unresolved resonance region of the capture yield. Maxwellian averaged cross sections were calculated in the temperature range of kT = 5 – 100 keV, and their astrophysical implications were investigate
Measurement of the 70Ge(n,Îł) cross section up to 300 keV at the CERN n_TOF facility
Neutron capture data on intermediate mass nuclei are of key importance to nucleosynthesis in the weak component of the slow neutron capture processes, which occurs in massive stars. The (n,γ) cross section on 70Ge, which is mainly produced in the s process, was measured at the neutron time-of-flight facility n_TOF at CERN. Resonance capture kernels were determined up to 40 keV neutron energy and average cross sections up to 300 keV. Stellar cross sections were calculated from kT =5 keV tokT =100 keV and are in very good agreement with a previous measurement by Walter and Beer (1985) and recent evaluations. Average cross sectionsareinagreementwithWalterandBeer(1985)overmostoftheneutronenergyrangecovered,whilethey aresystematicallysmallerforneutronenergiesabove150keV.Wehavecalculatedisotopicabundancesproduced in s-process environments in a 25 solar mass star for two initial metallicities (below solar and close to solar). While the low metallicity model reproduces best the solar system germanium isotopic abundances, the close to solar model shows a good global match to solar system abundances in the range of mass numbers A=60–80.Austrian Science Fund J3503Adolf Messer Foundation ST/M006085/1European Research Council ERC2015-StGCroatian Science Foundation IP-2018-01-857
Neutron capture cross sections of 69Ga and 71Ga at 25 keV and e peak = 90 keV
This project was supported by EFNUDAT, ERINDA, the EuroGENESIS project MASCHE, HIC for FAIR and BMBF (05P15RFFN1).We measured the neutron capture cross sections of 69Ga and 71Ga for a quasi-stellar spectrum at kBT = 25 keV and a spectrum with a peak energy at 90 keV by the activation technique at the Joint Research Centre (JRC) in Geel, Belgium. Protons were provided by an electrostatic Van de Graaff accelerator to produce neutrons via the reaction 7Li(p,n). The produced activity was measured via the Îł emission of the product nuclei by high-purity germanium detectors. We present preliminary results.publishersversionpublishe
First Measurement of the Ru(p,)Rh Cross Section for the p-Process with a Storage Ring
This work presents a direct measurement of the Ru()Rh cross section via a novel technique using a storage ring,
which opens opportunities for reaction measurements on unstable nuclei. A
proof-of-principle experiment was performed at the storage ring ESR at GSI in
Darmstadt, where circulating Ru ions interacted repeatedly with a
hydrogen target. The Ru()Rh cross section between 9
and 11 MeV has been determined using two independent normalization methods. As
key ingredients in Hauser-Feshbach calculations, the -ray strength
function as well as the level density model can be pinned down with the
measured () cross section. Furthermore, the proton optical potential
can be optimized after the uncertainties from the -ray strength
function and the level density have been removed. As a result, a constrained
Ru()Rh reaction rate over a wide temperature range is
recommended for -process network calculations.Comment: 10 pages, 7 figs, Accepted for publication at PR
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