Fast-neutron inelastic-scattering cross sections for the principal even-even actinide nuclei. II.<sup>238</sup>U(n,n')

Sheldon, Eric; Beghian, L. E.; Chan, D W S; Chang, Allen C.; Couchell, G.P.; Egan, J. J.; Goswami, G; Kegel, G. H. R.; Li, S Q; Mittler, A.; Pullen, D.J.; Schier, W.A.; Shao, J. Q.; Wang, A

doi:10.1088/0305-4616/12/5/009

Cited by 8 publications

(14 citation statements)

References 32 publications

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“…Many approximations were suggested and used; it was customary to couple only a few levels (usually three) of the ground-state rotational band in those calculations. In 2004 two of the authors studied the convergence of neutron cross sections on 238 U as a function of the number of coupled target states in the ground-state rotational band. It was shown that the common practice of calculating neutron cross sections with three coupled levels in K = 0 + ground-state bands is inadequate [7].…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, low-lying rotational bands, built on vibrational bandheads for even-even targets, and on single-particle bandheads for odd-A targets, need to be taken into account to describe neutron inelastic scattering on actinides. This fact has long been recognized for even-even nuclei; a vibrational-rotational description within the coupled-channels approach has been used to describe scattering data on even-even actinides by University of Lowell group [9][10][11] and later used by Kawano et al [12], Minsk group [13,14], and Bruyères-le-Châtel group (e.g., Refs. [15,16]).…”

Section: Introductionmentioning

confidence: 99%

“…However, authors are not aware of similar published work undertaken for odd actinides, 1 for which typically only the ground-state rotational band had been considered in opticalmodel studies. 2 Additionally, those works used nondispersive potentials to describe scattering data, except the dispersive potential used to describe neutron scattering on 238 U target [15] and other actinides [16].…”

Section: Introductionmentioning

confidence: 99%

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Nucleon scattering on actinides using a dispersive optical model with extended couplings

et al. 2016

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The Tamura coupling model [Rev. Mod. Phys. 37, 679 (1965)] has been extended to consider the coupling of additional low-lying rotational bands to the ground-state band. Rotational bands are built on vibrational bandheads (even-even targets) or single-particle bandheads (odd-A targets) including both axial and nonaxial deformations. These additional excitations are introduced as a perturbation to the underlying axially symmetric rigid-rotor structure of the ground-state rotational band. Coupling matrix elements of the generalized optical model are derived for extended multiband transitions in even-even and odd-A nuclei. Isospin symmetric formulation of the optical model is employed. A coupled-channels optical-model potential (OMP) containing a dispersive contribution is used to fit simultaneously all available optical experimental databases including neutron strength functions for nucleon scattering on 232 Th, 233,235,238 U, and 239 Pu nuclei. Quasielastic (p,n) scattering data on 232 Th and 238 U to the isobaric analog states of the target nucleus are also used to constrain the isovector part of the optical potential. Lane consistent OMP is derived for all actinides if corresponding multiband coupling schemes are defined. For even-even (odd-A) actinides almost all low-lying collective levels below 1 MeV (0.5 MeV) of excitation energy are coupled. OMP parameters show a smooth energy dependence and energy-independent geometry. A phenomenological optical-model potential that couples multiple bands in odd-A actinides is published for a first time. Calculations using the derived OMP potential reproduce measured total cross-section differences between several actinide pairs within experimental uncertainty for incident neutron energies from 50 keV up to 150 MeV. The importance of extended coupling is studied. Multiband coupling is stronger in even-even targets owing to the collective nature of the coupling; the impact of extended coupling on predicted compound-nucleus formation cross section reaches 5% below 3 MeV of incident neutron energy. Excitation of multiple bands in odd-A targets is weaker owing to the single-particle nature of the coupling. Coupling of ground-state rotational band levels in odd-A nuclei is sufficient for a good description of the compound-nucleus formation cross sections as long as the coupling is saturated (a minimum of seven coupled levels are typically needed).

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nucleon scattering on actinides using a dispersive optical model with extended couplings

et al. 2016

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“…While the nuclear structure of eveneven actinides below 500 keV corresponds to a rigid rotor, above 500 keV several vibrational bands are observed in the excited spectrum that are much better described by the soft rotor. This fact has long been recognized, a vibrational-rotational description within the coupled-channel approach have been used to describe data by several authors [13][14][15][16]. We propose a new solution to the problem derived from the soft-rotator description of the low-lying nuclear structure of actinides, but consistent with the rigid-rotor behaviour at low excitation energies.…”

Section: Nuclear Shapes and Coupling Potential Multipoles For Even-evmentioning

confidence: 90%

A dispersive optical model potential for nucleon induced reactions on²³⁸U and²³²Th nuclei with full coupling

Quesada

Soukhovitskiĩ

Capote

et al. 2013

EPJ Web of Conferences

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Abstract.A dispersive coupled-channel optical model potential (DCCOMP) that couples the ground-state rotational and low-lying vibrational bands of 238 U and 232 Th nuclei is studied. The derived DCCOMP couples almost all excited levels below 1 MeV of excitation energy of the corresponding even-even actinides. The ground state, octupole, beta, gamma, and non-axial bands are coupled. The first two isobar analogue states (IAS) populated in the quasi-elastic (p,n) reaction are also coupled in the proton induced calculation, making the potential approximately Lane consistent. The coupled-channel potential is based on a soft-rotor description of the target nucleus structure, where dynamic vibrations are considered as perturbations of the rigid rotor underlying structure. Matrix elements required to use the proposed structure model in Tamura coupled-channel scheme are derived. Calculated ratio R(U238/T h232) of the total cross-section difference to the averaged σ T for 238 U and 232 Th nuclei is shown to be in excellent agreement with measured data.

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“…Therefore low-lying rotational bands, built on vibrational band-heads for even-even and on single-particle bandheads for odd nuclei, need to be taken into account to describe neutron inelastic scattering on actinides. Authors were not able to find published optical model potentials for neutron scattering on odd actinides, even if many publications described applications to even-even actinides [3][4][5][6][7][8][9] dependent optical model potential for actinides [10][11][12] assuming a rigid rotor coupling of levels in the rotational ground state band. The coupling of vibrational bands improved the description of neutron scattering on even-even actinides in the energy region from 500 keV up to about 3 MeV, which is critical for fast neutron fission reactors, as was discussed at the WONDER 2012 workshop [13].…”

Section: Introductionmentioning

confidence: 99%

A Lane consistent optical model potential for nucleon scattering on actinide nuclei with extended coupling

Quesada

Capote

Soukhovitski

et al. 2016

EPJ Web of Conferences

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Abstract. An extension for odd-A actinides of a previously derived dispersive coupledchannel optical model potential (OMP) for 238 U and 232 Th nuclei is presented. It is used to fit simultaneously all the available experimental databases including neutron strength functions for nucleon scattering on 232 Th , 233,235,238 U and 239 Pu nuclei. Quasi-elastic (p,n) scattering data on 232 Th and 238 U to the isobaric analogue states of the target nucleus are also used to constrain the isovector part of the optical potential. For even-even (odd) actinides almost all low-lying collective levels below 1 MeV (0.5 MeV) of excitation energy are coupled. OMP parameters show a smooth energy dependence and energy independent geometry.

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Fast-neutron inelastic-scattering cross sections for the principal even-even actinide nuclei. II.²³⁸U(n,n')

Cited by 8 publications

References 32 publications

Nucleon scattering on actinides using a dispersive optical model with extended couplings

Nucleon scattering on actinides using a dispersive optical model with extended couplings

A dispersive optical model potential for nucleon induced reactions on²³⁸U and²³²Th nuclei with full coupling

A Lane consistent optical model potential for nucleon scattering on actinide nuclei with extended coupling

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Fast-neutron inelastic-scattering cross sections for the principal even-even actinide nuclei. II.238U(n,n')

Cited by 8 publications

References 32 publications

Nucleon scattering on actinides using a dispersive optical model with extended couplings

Nucleon scattering on actinides using a dispersive optical model with extended couplings

A dispersive optical model potential for nucleon induced reactions on238U and232Th nuclei with full coupling

A Lane consistent optical model potential for nucleon scattering on actinide nuclei with extended coupling

Contact Info

Product

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Fast-neutron inelastic-scattering cross sections for the principal even-even actinide nuclei. II.²³⁸U(n,n')

A dispersive optical model potential for nucleon induced reactions on²³⁸U and²³²Th nuclei with full coupling