R.W. Finlay

Neutron emission cross sections on 184W at 11.5 and 26 MeV and the neutron-nucleus scattering mechanism☆

Abstract Inelastic neutron emission at 11.5 and 26 MeV incident energies has been studied for monoisotopic sample of 184 W. Time-of-flight spectra were taken at several angles between 12° and 160° using a beam-swinger spectrometer. The data are averaged over 1 MeV energy bins and compared with the quantum-mechanical statistical multistep calculations

Neutron emission cross sections at low bombarding energies and the novelty in multistep compound reaction model

Abstract Inelastic neutron emission at 6.7 and 20 MeV incident energies has been measured for monoisotopic samples of 165 Ho and 181 Ta. Time-of-flight spectra were taken at several angles between 15° and 145° using a beam-swinger spectrometer. The cross sections are averaged over 1 MeV energy bins. The 20 MeV data, when compared with the quantum-mechanical statistical multistep calculations have revealed a magnitude problem in the existing theories. A gradual or “multistep” absorption in the entrance channels is proposed as a way out of the difficulty. This modification turns out to be sufficient for an adequate description of the experimental data.

Neutron emission cross sections on 93Nb and 209Bi at 20 MeV incident energy

Abstract Double-differential neutron emission cross sections at 20 MeV incident energy have been studied for monoisotopic samples of 93Nb and 209Bi. Time-of-flight spectra were taken at several angles between 15° and 153° using a beam-swinger spectrometer. The data are averaged over 0.5 MeV energy bins and compared with quantum-mechanical, statistical multistep calculations.

Nucleon elastic scattering from 40Ca between 11 and 48 MeV

Abstract Differential cross sections for the elastic scattering of neutrons from 40Ca have been measured in the 19–26 MeV region. The neutron elastic scattering data, previous neutron measurements and additional proton elastic scattering data are analyzed using three different approaches to the optical model potential: Woods-Saxon parameterization, model independent analysis and microscopic calculations. The difference between the phenomenological neutron and proton real potentials is studied in terms of Coulomb effects, nuclear polarization and charge symmetry breaking in the nuclear mean field.

Neutron scattering cross sections and partial kerma values for oxygen, nitrogen and calcium at 18<En<60 MeV

Recent measurements of differential elastic and inelastic neutron scattering from oxygen, nitrogen and calcium at 18 less than En less than 26 MeV are presented and analysed in terms of the optical model. These data, together with earlier measurements of scattering and total cross sections, are used to construct model potentials that may be used to calculate various quantities of interest in neutron dosimetry in an energy region (20-60 MeV) where very few cross section data are available. The heavy-ion-recoil contribution to kerma is obtained directly from the data at each energy. The value of proton inelastic scattering data for validating potential models at high energy is discussed.

Anomalous behavior of the n + 208Pb potential near the fermi energy☆

New measurements of elastic neutron scattering from 208Pb and 209Bi at En < 7 MeV have revealed the detailed shape of the Fermi surface anomaly in the nucleon-nucleus potential in an energy region inaccessible by proton scattering. The resulting energy dependence of the real potential strongly supports recent dispersion-theory corrections to the Hartree-Fock mean field.

Nucleon-induced excitation of collective bands in 12C

Abstract Detailed differential elastic and inelastic neutron scattering data for 12 C at E n = 20–26 MeV are presented and analyzed in terms of a deformed optical potential and rotation-vibration interaction in a coupled-channel formalism. All well-established states in 12 C up to 15 MeV excitation energy are observed in the experiment. Additional neutron scattering, total and reaction cross-section data for 20 E n K π assignments for some excited bands in 12 C.

Empirical determination of the mean free path of a nucleon in the nuclear medium

Abstract The mean free path of a nucleon in the nuclear medium extracted from measured neutron-nucleus total cross sections is compared with the values determined from the energy-momentum dispersion relation. The optical potentials used in the dispersion relation are the relativistic global energy-dependent Lorentz scalar and vector potentials of Dirac phenomenology. Excellent agreement between the values extracted from either total neutron-nucleus cross sections or proton-nucleus reaction cross sections and the calculated values is achieved when the optical potentials are evaluated using radial values corresponding to approximately 80% of nuclear matter density.

Elastic and inelastic scattering of nucleons from 16O

Abstract Measurements of differential elastic and inelastic cross sections for neutron scattering from 16O at incident energies 18 to 26 MeV are presented. In addition to cross sections for neutron scattering differential cross sections for proton scattering up to 66 MeV are described in terms of phenomenological optical model potentials. At 24.5 MeV incident energy inelastic scattering up to 11.5 MeV excitation was measured. The elastic and inelastic compound nucleus contributions were examined. Direct inelastic scattering from the normal parity states was calculated using the DWBA and coupled-channel formalisms. The inelastic scattering cross section from non-normal parity state 2− was calculated using the coupled-channel formalism via multi-step processes. Cross sections due to inelastic scattering from some of the states, which are thought to be members of an excited state rotational band were calculated using both vibrational and rotational approaches and were compared.

Nucleon induced excitation of Kπ=0+, 0+2, 1− and 3− bands in 12C

Elastic and inelastic neutron scattering from /sup 12/C is studied in a coupled-channel approach. (AIP)Elastic and inelastic neutron scattering from 1 2 C is studied in a coupled‐channel approach. (AIP)