Comparisons between various width fluctuation correction factors for compound nucleus reactions

Hilaire, Stéphane; Lagrange, Ch.; Koning, A. J.

doi:10.1016/s0003-4916(03)00076-9

Cited by 71 publications

(68 citation statements)

References 15 publications

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“…All energetically possible final channels χ have to be taken into account, thus the denominator includes contributions from decays to discrete levels in the residual nuclei (given by the first sum in the denominator, ) as well as contributions from decays to regions described by a level density in the residual nuclei (given by the second sum in the denominator which involves an energy integral of transmission coefficients and level densities in the residual nuclei). Width fluctuation corrections W αχ are included in order to account for correlations between the incident and outgoing reaction channels [5,6]. In writing Eq.…”

Section: Formalism For Compound-nuclear Capture Reactionsmentioning

confidence: 99%

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Compound-nuclear reactions with unstable nuclei: Constraining theory through innovative experimental approaches

Escher

Tonchev

Burke

et al. 2016

EPJ Web of Conferences

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Abstract. Cross sections for compound-nuclear reactions involving unstable targets are important for many applications, but can often not be measured directly. Several indirect methods have recently been proposed to determine neutron capture cross sections for unstable isotopes. We consider three approaches that aim at constraining statistical calculations of capture cross sections with data obtained from the decay of the compound nucleus relevant to the desired reaction. Each method produces this compound nucleus in a different manner (via a light-ion reaction, a photon-induced reaction, or β-decay) and requires additional ingredients to yield the sought-after cross section. We give a brief outline of the approaches and employ preliminary results from recent measurements to illustrate the methods. We discuss the main advantages and challenges of each approach.

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Section: Formalism For Compound-nuclear Capture Reactionsmentioning

confidence: 99%

“…2. At this point, the width fluctuation correlations can be included using standard correction factors [5,6,14].…”

Section: Cn Production Via Inelastic Scattering and Transfer Reactionmentioning

confidence: 99%

Compound-nuclear reactions with unstable nuclei: Constraining theory through innovative experimental approaches

Escher

Tonchev

Burke

et al. 2016

EPJ Web of Conferences

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“…Historical surrogate treatment assumes that customary in-out-going channel WFCF can be neglected (i.e ; W c,c' ≈1) although, by matter of fact, we know that this correction is substantial [4] for any open channels for excitation energies up to 2 MeV above neutron emission threshold (S n ) as far as actinide nuclides are concerned. According to fission decay, the amount of average cross section correction depends on both the number of fission channels involved and the magnitude of their average widths.…”

Section: Historical Surrogate Modelingmentioning

confidence: 99%

“…Eq. 9 then reduces to the following (10) 03003-p. 4 where is the entrance channel width related to the single particle stripped from the incident light particle (e.g; a dineutron for a (t,p) entrance vector) and transferred into corresponding sp-orbit of target nucleus that carries two neutrons less than the formed CN.…”

Section: Expected Wfcf Differences Between Surrogate-and Neutron-indumentioning

confidence: 99%

Monte Carlo simulation of transfer reactions using extended R-matrix theory picturing surrogate-type WFCF features

Bouland

2016

EPJ Web of Conferences

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Abstract. This article supplies an overview of issues related to the interpretation of surrogate measurement results for neutron-incident cross section predictions; difficulties that are somehow masked by the historical conversion route based on Weisskopf-Ewing approximation. Our proposal is to handle the various difficulties by using a more rigorous approach relying on Monte Carlo simulation of transfer reactions with extended R-matrix theory. The multiple deficiencies of the historical surrogate treatment are recalled but only one is examined in some details here; meaning the calculation of in-out-going channel Width Fluctuation Correction Factors (WFCF) which behavior witness partly the failure of Niels Bohr's compound nucleus theoretical landmark. Relevant WFCF calculations according to neutron-induced surrogate-and cross section-types as a function of neutron-induced fluctuating energy range [0 -2.1 MeV] are presented and commented in the case of the 240 Pu * and 241 Pu * compound nucleus isotopes.

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“…This causes an elastic enhancement. To account for these deviations, width fluctuation corrections can be introduced in the HF formalism by different approximate expressions [3].…”

Section: Introductionmentioning

confidence: 99%

Improved predictions of nuclear reaction rates for astrophysics applications with the TALYS reaction code

Goriely

Hilaire

Koning

2007

Nd2007

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Abstract. Nuclear reaction rates for astrophysics applications are traditionally determined on the basis of HauserFeshbach reaction codes, like MOST. These codes use simplified schemes to calculate the capture reaction cross section on a given target nucleus, not only in its ground state but also on the different thermally populated states of the stellar plasma at a given temperature. Such schemes include a number of approximations that have never been tested, such as an approximate width fluctuation correction, the neglect of delayed particle emission during the electromagnetic decay cascade or the absence of the pre-equilibrium contribution at increasing incident energies. New developments have been brought to the reaction code TALYS to estimate the Maxwellian-averaged reaction rates of astrophysics relevance. These new developments give us the possibility to calculate with an improved accuracy the reaction cross sections and the corresponding astrophysics rates. The TALYS predictions for the thermonuclear rates of astrophysics relevance are presented and compared with those obtained with the MOST code on the basis of the same nuclear ingredients for nuclear structure properties, optical model potential, nuclear level densities and γ-ray strength. It is shown that, in particular, the pre-equilibrium process significanly influences the astrophysics rates of exotic neutron-rich nuclei. The reciprocity theorem traditionally used in astrophysics to determine photorates is also shown no to be valid for exotic nuclei. The predictions obtained with different nuclear inputs are also analyzed to provide an estimate of the theoretical uncertainties still affecting the reaction rate prediction far away from the experimentally known regions.

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Comparisons between various width fluctuation correction factors for compound nucleus reactions

Cited by 71 publications

References 15 publications

Compound-nuclear reactions with unstable nuclei: Constraining theory through innovative experimental approaches

Compound-nuclear reactions with unstable nuclei: Constraining theory through innovative experimental approaches

Monte Carlo simulation of transfer reactions using extended R-matrix theory picturing surrogate-type WFCF features

Improved predictions of nuclear reaction rates for astrophysics applications with the TALYS reaction code

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