Complete calculation of evaluated Maxwellian-averaged cross sections and their errors for s-process nucleosynthesis (original) (raw)
Related papers
Present contribution represents a significant improvement of our previous calculation of Maxwellian-averaged cross sections and astrophysical reaction rates. Addition of newlyevaluated neutron reaction libraries, such as ROSFOND and Low-Fidelity Covariance Project, and improvements in data processing techniques allowed us to extend it for entire range of sprocess nuclei, calculate Maxwellian-averaged cross section uncertainties for the first time, and provide additional insights on all currently available neutron-induced reaction data. Nuclear reaction calculations using ENDF libraries and current Java technologies will be discussed and new results will be presented.
Springer Proceedings in Physics, 2019
We investigated the impact of uncertainties in neutron-capture and weak reactions (on heavy elements) on the s−process nucleosynthesis in low-mass stars using a Monte-Carlo based approach. We performed extensive nuclear reaction network calculations that include newly evaluated temperature-dependent upper and lower limits for the individual reaction rates. Our sophisticated approach is able to evaluate the reactions that impact more significantly the final abundances. We found that β-decay rate uncertainties affect typically nuclides near s-process branchings, whereas most of the uncertainty in the final abundances is caused by uncertainties in neutron capture rates, either directly producing or destroying the nuclide of interest. Combined total nuclear uncertainties due to reactions on heavy elements are approximately 50%.
Nuclear Physics of the s Process
Publications of the Astronomical Society of Australia, 2008
Starting from a sketch of the s-process concept formulated 50 years ago, the nuclear physics data for s-process calculations are briefly reviewed with emphasis on the status of neutron capture cross sections and beta decay rates. Accurate and comprehensive experimental data are mandatory as direct input for s-process calculations as well as for improving the complementary information from nuclear theory. The current challenges of the field are discussed in the light of new or optimized methods and state-of-theart facilities, indicating the potential for accurate measurements and the possibility to study cross sections of radioactive isotopes. These opportunities will be considerably enriched by the enormous improvements provided by new facilities.
Impact of nuclear mass measurements in the vicinity of 132Sn on the r-process nucleosynthesis
HNPS Advances in Nuclear Physics
Nuclear masses are a key aspect in the modelling of nuclear reaction rates for the r-process nucleosynthesis. High precision mass measurements drastically reduce the associated uncertainties in the modelling of r-process nucleosynthesis. We investigate the impact of nuclear mass uncertainties on neutron-capture rates calculations using a Hauser – Feshbach statistical code in the vicinity of 132Sn. Finally, we study the impact of the propagated neutron-capture reaction rates uncertainties on the r-process nucleosynthesis. We find that mass measurements with uncertainties higher than 20 keV affect the calculation of reaction rates. We also note that modelling of reaction rates can differ for more than a factor of two even for experimentally known nuclear masses.
Experimental Studies of Nuclear Physics Input for \(\gamma \)-Process Nucleosynthesis
Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016), 2017
The predictions of reaction rates for the γ process in the scope of the Hauser-Feshbach statistical model crucially depend on nuclear physics input-parameters as optical-model potentials (OMP) or γ-ray strength functions. Precise cross-section measurements at astrophysically relevant energies help to constrain adopted models and, therefore, to reduce the uncertainties in the theoretically predicted reaction rates. During the last years, several cross-sections of charged-particle induced reactions on heavy nuclei have been measured at the University of Cologne. Either by means of the in-beam method at the HORUS γ-ray spectrometer or the activation technique using the Cologne Clover Counting Setup, total and partial cross-sections could be used to further constrain different models for nuclear physics input-parameters. It could be shown that modifications on the α-OMP in the case of the 112 Sn(α,γ) reaction also improve the description of the recently measured cross sections of the 108 Cd(α,γ) and 108 Cd(α,n) reaction and other reactions as well. Partial cross-sections of the 92 Mo(p, γ) reaction were used to improve the γ-strength function model in 93 Tc in the same way as it was done for the 89 Y(p,γ) reaction.
montage: AGB Nucleosynthesis with Full s-Process Calculations
Publications of the Astronomical Society of Australia, 2009
We present montage, a post-processing nucleosynthesis code that combines a traditional network for isotopes lighter than calcium with a rapid algorithm for calculating the s-process nucleosynthesis of the heavier isotopes. The separation of those parts of the network where only neutron-capture and beta-decay reactions are significant provides a substantial advantage in computational efficiency. We present the yields for a complete set of s-process isotopes for a 3 M⊙, Z = 0.02 stellar model, as a demonstration of the utility of the approach. Future work will include a large grid of models suitable for use in calculations of Galactic chemical evolution.
ND2007, 2007
The paper deals with the investigation of the uncertainty associated to the calculation of activation and transmutation cross sections for neutron and proton induced reactions. Results of the calculations performed by means of the TALYS code and the ALICE/ASH code with different models for the description of the nuclear level densities have been extensively compared with EXFOR experimental data. Statistical deviation factors quantifying the discrepancy between experimental and theoretical results have been obtained, which can be used to define appropriate models for the nuclear reaction cross section calculation for different mass range of target nuclei. Furthermore, experimental data have been also compared against the most modern nuclear data files in order to investigate the gain in accuracy one should expect from the evaluation work with respect to the data obtained via nuclear model calculation.
Impacts of nuclear-physics uncertainties in the s-process determined by Monte-Carlo variations
arXiv (Cornell University), 2018
The s-process, a production mechanism based on slow-neutron capture during stellar evolution, is the origin of about half the elements heavier than iron. Abundance predictions for s-process nucleosynthesis depend strongly on the relevant neutron-capture and β-decay rates, as well as on the details of the stellar model being considered. Here, we have used a Monte-Carlo approach to evaluate the nuclear uncertainty in s-process nucleosynthesis. We considered the helium burning of massive stars for the weak s-process and low-mass asymptotic-giant-branch stars for the main s-process. Our calculations include a realistic and general prescription for the temperature dependent uncertainty for the reaction cross sections. We find that the adopted uncertainty for (n, γ) rates, tens of per cent on average, effects the production of s-process nuclei along the line of β-stability, and that the uncertainties in β-decay from excited state contributions, has the strongest impact on branching points.
Current quests in nucleosynthesis: Present and future neutron-induced reaction measurements
2014
We present some open questions in nucleosynthesis focused on the measurement of relevant neutron capture cross-sections and on new experimental methods. We review the recent 63 Ni(n,γ) experiment carried out at the n_TOF facility at CERN and its astrophysical implications as well as future experiments and opportunities at n_TOF. We argue some improvements in the measurement of cross-sections by activation arising from a new method for the generation of stellar neutron spectra. We show preliminary results of the experimental validation of the method. We discuss the astrophysical implications of the 181 Ta(n,γ) stellar cross-section measured with this method. Finally, we describe challenging experiments consisting of in situ radioactive ion beams and stellar neutron beams.