AZURE: An<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>R</mml:mi></mml:mrow></mml:math>-matrix code for nuclear astrophysics

Azuma, R.E.; Uberseder, E.; Simpson, E. C.; Brune, C. R.; Costantini, H.; Boer, Robert J. de; Görres, J.; Heil, M.; LeBlanc, P. J.; Ugalde, C.; Wiescher, M.

doi:10.1103/physrevc.81.045805

Cited by 248 publications

(311 citation statements)

References 54 publications

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“…In fact, when direct experimental data are not available, the existence of unknown resonance and/or the correct evaluation of resonance parameters and/or interference pattern between different resonances may dramatically change the cross section extrapolations. A general discussion of techniques that extrapolate the cross sections is beyond the aims of this paper (interested readers may refer to Azuma et al 2010). Nevertheless, in the cases where the direct experimental data are relatively close to the Gamow peak energies, the experimental uncertainties may represent a fair description of the reaction rate uncertainties also at relevant energies.…”

Section: Reaction Rate Uncertaintiesmentioning

confidence: 99%

Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities

Cristallo

Leva

Imbriani

et al. 2014

A&A

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Context. The origin of fluorine is a longstanding problem in nuclear astrophysics. It is widely recognized that asymptotic giant branch (AGB) stars are among the most important contributors to the Galactic fluorine production. Aims. In general, extant nucleosynthesis models overestimate the fluorine production by AGB stars with respect to observations. Although those differences are rather small at solar metallicity, low metallicity AGB stellar models predict fluorine surface abundances up to one order of magnitude larger than the observed ones. Methods. As part of a project devoted to reducing the uncertainties in the nuclear physics that affect the nucleosynthesis in AGB stellar models, we review the relevant nuclear reaction rates involved in the fluorine production or destruction. We perform this analysis on a model with initial mass M = 2 M and Z = 0.001. Results. We found that the major uncertainties are due to the 13 C(α,n) 16 O, the 19 F(α,p) 22 Ne, and the 14 N(p,γ) 15 O reactions. A change in the corresponding reaction rates within the present experimental uncertainties implies surface 19 F variations at the AGB tip lower than 10%, thus much smaller than observational uncertainties. For some α capture reactions, however, cross sections at astrophysically relevant energies are determined on the basis of nuclear models, in which some low-energy resonance parameters are very poorly known. Thus, larger variations in the rates of those processes cannot be excluded. That being so, we explore the effects of the variation in some α capture rates well beyond the current published uncertainties. The largest 19 F variations are obtained by varying the 15 N(α,γ) 19 F and the 19 F(α,p) 22 Ne reactions. Conclusions. The currently estimated uncertainties of the nuclear reaction rates involved in the production and destruction of fluorine produce minor 19 F variations in the ejecta of AGB stars. Analysis of some α capture processes that assume a wider uncertainty range determines 19 F abundances in better agreement with recent spectroscopic fluorine measurements at low metallicity. In the framework of this scenario, the 15 N(α,γ) 19 F and the 19 F(α,p) 22 Ne reactions show the strongest effects on fluorine nucleosynthesis. The presence of poorly known low-energy resonances make such a scenario possible, even if it is unlikely. We plan to measure these resonances directly.

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Section: Reaction Rate Uncertaintiesmentioning

confidence: 99%

Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities

Cristallo

Leva

Imbriani

et al. 2014

A&A

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“…A detailed description of the original AZURE code and the underlying R-matrix theory can be found in Refs. [41,42] and references therein. The present code has taken the computational concepts and physics of the original code and reimplemented them in an object oriented approach using C++.…”

Section: R-matrix Approachmentioning

confidence: 99%

“…An R-matrix code, based on the principles developed for the code AZURE [41], is used for the present analysis. A detailed description of the original AZURE code and the underlying R-matrix theory can be found in Refs.…”

Section: R-matrix Approachmentioning

confidence: 99%

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R-matrix analysis of16O compound nucleus reactions

et al. 2013

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Background Over the last 60 years, a large amount of experimental nuclear data has been obtained for reactions which probe the 16 O compound nucleus near the alpha and proton separation energies, the energy regimes most important for nuclear astrophysics. Difficulties and inconsistencies in R-matrix fits of the individual reactions prompt a more complete analysis.Purpose Determine the level of consistency between the wide variety of experimental data using a multiple entrance/exit channel R-matrix framework. Using a consistent set of data from multiple reaction channels, attain an improved fitting for the 15 N(p, γ0) 16 O reaction data.Methods Reaction data for all available reaction channels were fit simultaneous using a multichannel R-matrix code.Results Over the wide range of experimental data considered, a high level of consistency was found, resulting in a single consistent R-matrix fit which described the broad level structure of 16 O below Ex = 13.5 MeV. The resulting fit was used to extract an improved determination of the low energy S-factor for the reactions 15 N(p, γ) 16 O and 15 N(p, α) 12 C. ConclusionThe feasibility and advantages of a complete multiple entrance/exit channel R-matrix description for the broad level structure of 16 O has been achieved. A future publication will investigate the possible effects of the multiple channel analysis on the reaction 12 C(α, γ) 16 O.

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“…Hale [3], and R.E. Azuma [4], S. Kunieda [5] Lithium is widely used in reactor design and analysis. Neutron inducing 6 Li can produce tritium, and the cross section of 6 Li(n,t) below 1.7 MeV is a standard cross section.…”

Section: Introductionmentioning

confidence: 99%

Theoretical calculations and analysis for n + ⁶Li reaction

2017

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Abstract. R-matrix theory is an important methodology for applications on light, medium and heavy mass nuclides nuclear reaction in the resonance energy range. Full R-matrix formalism contains the diagonal elements of the energy levels matrix and it is a rigorous theory. Because of different assumptions and approximations, many kinds of R-matrix derived methods are obtained. The new R-matrix code FDRR is presented and includes 4 kinds of R-matrix applications. It can be used for calculating integral cross sections and angular distributions of 2-bodies reactions. The cross sections and angular distributions of n+ 6 Li reaction are calculated and analyzed by FDRR code. The results are in good agreement with experimental data below 20 MeV.

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AZURE: AnR-matrix code for nuclear astrophysics

Cited by 248 publications

References 54 publications

Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities

Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities

R-matrix analysis of16O compound nucleus reactions

Theoretical calculations and analysis for n + ⁶Li reaction

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AZURE: AnR-matrix code for nuclear astrophysics

Cited by 248 publications

References 54 publications

Effects of nuclear cross sections on19F nucleosynthesis at low metallicities

Effects of nuclear cross sections on19F nucleosynthesis at low metallicities

R-matrix analysis of16O compound nucleus reactions

Theoretical calculations and analysis for n + 6Li reaction

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Product

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Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities

Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities

Theoretical calculations and analysis for n + ⁶Li reaction