Coupled-channel Optical Model Potential Research Articles

Coupled-channel analysis of deuteron scattering on 56Fe

The deuteron elastic and inelastic scattering on 56Fe is calculated by using the coupled-channel method and the collective motion models. Based on the experimental angular distributions of scattering processes, an optimal set of parameters are obtained for the deuteron's coupled-channel optical model potential and 56Fe's deformation including first ten low-lying excited states. The calculation results are in good agreement with the experimental data at low incident energies (Ed < 30 MeV), except for 41+(2.085 MeV) and 23+(2.960 MeV), and the deviation is found for several states at 56 MeV. That indicates further analyses and discussions are necessary.

The neutron transmission of natFe, 197Au and natW

Neutron total cross sections of natFe, 197Au and natW have been measured at the n ELBE neutron time-of-flight facility in the energy range 0.15-8MeV with an uncertainty due to counting statistics of up to 2% and a total uncertainty due to systematic effects of 1%. The neutrons are produced with the superconducting electron accelerator ELBE using a liquid lead circuit as photo-neutron target. By periodical sample-in-sample-out measurements the transmission of the sample materials has been determined using a low-threshold plastic scintillation detector. The resulting effective total cross sections show good agreement with previously measured data that cover only part of the energy range available at n ELBE. The results have also been compared to evaluated library files and recent calculations based on a dispersive coupled channel optical model potential.

Evaluation of cross sections for neutron interactions with 238U in the energy region between 5 keV and 150 keV

.Cross sections for neutron interactions with 238U in the energy region from 5keV to 150keV have been evaluated. Average total and capture cross sections have been derived from a least squares analysis using experimental data reported in the literature. The resulting cross sections have been parameterised in terms of average resonance parameters maintaining full consistency with results of optical model calculations by using a dispersive coupled channel optical model potential. The average compound partial cross sections have been expressed in terms of transmission coefficients by applying the Hauser-Feshbach statistical reaction theory including width-fluctuations. A generalized single-level representation compatible with the energy-dependent options of the ENDF-6 format has been applied using standard boundary conditions. The results have been transferred into a full ENDF-6 compatible data file.

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

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.

Results of total cross section measurements for 197Au in the neutron energy region from 4 to 108 keV at GELINA

Transmission measurements have been performed to determine the total cross section for neutron-induced reactions with 197Au in the energy region from 4keV to 108keV. The experiments were carried out at a 50m measurement station of the time-of-flight facility GELINA using a 6Li glass scintillator. The average total cross section as a function of neutron energy was derived after correcting the observed average transmission for cross section fluctuations due to resonance structures. The results have been compared with literature data and with the total cross section resulting from a dispersive coupled-channel optical model potential. The neutron strength function for s -wave neutrons and an orbital-independent scattering radius, together with their covariance matrix, have been derived in the neutron energy region between 4keV and 108keV through a parameterization of the total cross section based on a nuclear reaction theory.

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

A dispersive coupled-channel optical model potential (DCCOMP) that cou- ples 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 exci- tation 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) popu- lated 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 de- rived. Calculated ratio R(U238=T h232) of the total cross-section di erence to the aver- aged T for 238 U and 232 Th nuclei is shown to be in excellent agreement with measured data.

A global dispersive coupled-channel potential for the A = 24–122 mass range up to 200 MeV

A global dispersive coupled-channel optical model potential for the mass range of A = 24–122 is constructed up to 200 MeV incident energies. The local parameters for seven individual nuclei are searched by using the coupled-channel method based on the rigid-rotator model. The global forms of potential parameters are obtained by fitting those local parameters with simple functional forms of the target mass number. The numerical calculations show good agreement with available experimental data for neutron total cross sections, proton reaction cross sections, neutron/proton elastic and inelastic angular distributions, and proton elastic and inelastic analyzing powers.

A Global Dispersive Coupled-Channel Optical Model Potential for Actinides

A global dispersive coupled-channel optical model (DCCOM) potential is proposed to describe neutron and proton interactions with actinide nuclei in the 0.001 to 200MeV range. A linear dependence of the geometrical parameters on the mass number A is employed, and deformation parameters are adjusted for each nucleus to extend the DCCOM determined previously for 238U and 232Th to neighboring nuclei, 237Np, 241Am, 242,240,239Pu, and 235,233U. Fitted deformations are in reasonable agreement with those derived theoretically. The present DCCOM is capable of describing not only the cross sections but also the total cross section differences between 232Th and 238U up to 200 MeV within experimental uncertainty, verifying that the isovector potential and assumed geometrical parameters are adequate for describing the minute difference between the cross sections of actinide nuclei and their energy dependence. The present results are compared with calculations obtained using non-dispersive potentials frequently employed in this mass range to reveal the advantage of employing a dispersion relation.

A Global Dispersive Coupled-Channel Optical Model Potential for Actinides

A global dispersive coupled-channel optical model (DCCOM) potential is proposed to describe neutron and proton interactions with actinide nuclei in the 0.001 to 200MeV range. A linear dependence of the geometrical parameters on the mass number A is employed, and deformation parameters are adjusted for each nucleus to extend the DCCOM determined previously for 238U and 232Th to neighboring nuclei, 237Np, 241Am, 242,240,239Pu, and 235,233U. Fitted deformations are in reasonable agreement with those derived theoretically. The present DCCOM is capable of describing not only the cross sections but also the total cross section differences between 232Th and 238U up to 200 MeV within experimental uncertainty, verifying that the isovector potential and assumed geometrical parameters are adequate for describing the minute difference between the cross sections of actinide nuclei and their energy dependence. The present results are compared with calculations obtained using non-dispersive potentials frequently employed in this mass range to reveal the advantage of employing a dispersion relation.

Is a global coupled-channel dispersive optical model potential for actinides feasible?

An isospin-dependent coupled-channel optical model potential containing a dispersive term with a nonlocal contribution is used to simultaneously fit the available experimental database (including strength functions and scattering radius) for neutron and proton scattering on strongly deformed $^{238}\mathrm{U}$ and $^{232}\mathrm{Th}$ nuclei. The energy range 0.001--200 MeV is covered. A dispersive coupled-channel optical model (DCCOM) potential with parameters that show a smooth energy dependence and energy-independent geometry are determined from fits to the entire data set. Calculations using the obtained DCCOM potential reproduce measured total cross-section differences between $^{232}\mathrm{Th}$ and $^{238}\mathrm{U}$ within experimental uncertainty. The isovector terms and the observed very weak dependence of the geometrical parameters on mass number A allow us to extend the derived potential parameters to neighboring actinide nuclei with great confidence.

Dispersive coupled-channel analysis of nucleon scattering fromTh232up to 200 MeV

An isospin-dependent coupled-channels optical model potential containing a dispersive term (including nonlocal contribution) is used to simultaneously fit the available experimental database (including strength functions and scattering radius) for neutron and proton scattering on strongly deformed $^{232}\mathrm{Th}$ nucleus. The energy range 0.001--200 MeV is covered. A dispersive coupled-channel optical model potential with parameters that show a smooth energy dependence and energy independent geometry are determined from fits to the entire data set. Dispersive contribution is shown to be the dominant Coulomb correction to the proton real potential below the Coulomb barrier. Inclusion of nonlocality effects in the absorptive volume potential and its corresponding dispersive contribution to the real potential is needed to achieve an excellent agreement above 100 MeV.