New 23Na evaluation in the resolved resonance range taking into account both differential and double differential experiments

In 2012 CEA produced a entire new evaluation of sodium nuclear data for the release of the JEFF-3.2 evaluated nuclear data library. During the evaluation process performed with the CONRAD code, several differential measurements (total and discrete inelastic cross-sections) have been used. However double differential data (elastic angular distribution) that were yet available in the EXFOR database were not incorporated in the analysis at that time. The experimental elastic angular distribution were discarded because of it was impossible to obtain a good agreement for both angle-integrated cross-sections and double differential ones. The underlying cause of this disagreement is expected to be due to the attribution of quantum numbers to resonance and related channel amplitudes. Indeed these numbers are imposed during the analysis but impact differently angular distributions and angle-integrated cross-sections. An automated search for an accurate set of quantum numbers has been implemented in order to produce a reliable quantum numbers set. In this paper we present a new evaluation of Na-23 taking into account both differential and double differential measurements. The analysis performed with the CONRAD code reached the level of agreement with experimental data for the total and inelastic cross-sections but this time with a significant improvement for the elastic angular distributions. This new evaluation produced in the ENDF-6 format has then been tested and validated on critical facilities calculation (MASURCA and ZPPR) in different configurations (nominal and voided) in order to assess its performances.

Volume and surface nonlocality terms in the neutron–nucleus elastic scattering using the velocity-dependent optical potential

In this work, we tested the effect of adding a volume term to the surface term in our modified optical potential in the case of elastic neutron scattering of spin-zero 40Ca nucleus in the incident energy range between 30–50 MeV. This is achieved in two steps. First, we fit our theoretical elastic angular distribution scattering using the surface term in our velocity-dependent optical potential concerning the experimental data. Then, we adjust our theoretical elastic angular distribution scattering with the experimental data after adding the volume term into our velocity-dependent optical potential. The second step is comparing the two fits and noticing the effect of adding a volume term to the surface term. Clearly, the modified optical potential using the volume term resulted in excellent fits to the experimental data, most notably the pronounced large angle, backscattering minima, which depend sensitively on the incident energies and which have long been associated with nonlocalities. We assume the nonlocality to be due to interaction between the incident neutrons and the nucleons inside the target.

16O-NUCLEUS ELASTIC SCATTERING IN THE ENERGY RANGE 300 MeV–1.503 GeV

In this work we analyze the elastic angular distribution for the scattering of 16 O from 12 C , 16 O , 28 Si , 40 Ca , 90 Zr , and 208 Pb in the energy range 300 MeV–1.503 GeV within the framework of the Coulomb modified correlation expansion for the Glauber amplitude. Our calculations involve (i) up to the two-body density term in the correlation expansion, (ii) the realistic nuclear form factors, and (iii) the high q-components of the basic (input) NN amplitude. The results are found to provide a satisfactory explanation of the data in all the cases. Moreover, we could assess the energy dependence of the NN amplitude, and the trend of its slope strengthens the need of nondiffractive behavior of the NN amplitude in the energy range under consideration. We also show that the c.m. correlations play an important role in nucleus–nucleus collision.

SECOND-ORDER EIKONAL MODEL ANALYSIS OF16O+16OELASTIC SCATTERING

We analyze the elastic scattering angular distributions of the16O +16O system at Elab=480 MeV and 704 MeV within the framework of the second-order eikonal model based on Coulomb trajectories of colliding nuclei. The diffractive oscillatory structure observed in the elastic angular distribution could be explained due to the interference between the near- and far-side scattering amplitudes. The presence of a nuclear rainbow in this system is evidenced through a classical deflection function. The effective optical potential is developed from the second-order non-eikonal phase shifts.