Nuclear Level Density Model Research Articles

Nuclear level density as a tool for probing the inelastic scattering of 6He

The cross sections are calculated for the both elastic and inelastic scattering of 6He from 12C and 4He. A phenomenological optical potential is used to describe the elastic scattering. 4He is taken as spherical and inelastic couplings to the first excited states of 6He and 12C are described with collective rotational model and coupled-channels method. Deformation lengths for 6He and 12C are determined from semi-classical nuclear level density model by using Laplace-like formula for the nuclear level density parameter. The comparison of the predicted and the measured cross sections are presented to test the applicability of nuclear level density model to the light exotic nuclei reactions. Good agreement is achieved between the predicted and measured cross sections.

Excitation Function of 56Fe(n,α)53Cr Reaction from Threshold to 20 MeV for Fusion Applications

The current state of nuclear data evaluations requires improvement for fusion applications. In this context, the excitation function of the 56Fe(n,α)53Cr reaction from threshold to 20 MeV has been calculated using the Hauser-Feshbach statistical model with preequilibrium effects by the TALYS-1.4 code. Different types of nuclear level density models have been used in the calculation. The present calculations are compared with existing experimental data as well as with latest available evaluated nuclear data libraries ENDF/B-VII.1, JEFF-3.2, and JENDL-4.0. Good agreement between the calculated and the experimental data validates the nuclear model approaches with increased predictive power to supplement and extend the nuclear database. The present calculations have also been compared with the (n,α) reaction cross-section systematics at 14.5-MeV neutron energy.

Pre-equilibrium effects on (n,p) reactions of Gd and Dy isotopes from threshold to 20 MeV

The excitation functions of (n,p) reactions for the 13 stable isotopes of rare earth Gd and Dy elements are calculated using TALYS-1.4 code from threshold to 20MeV. The optimization of input parameters has been done before running the code. The global optical model potential for neutron and proton proposed by Koning and Delaroche has been adopted in the calculations. The cross-sections are calculated using Hauser Feshbach statistical model for compound nucleus contribution with constant temperature and Fermi gas nuclear level density model. The effect of pre-equilibrium has been checked by invoking different pre-equilibrium models in the code. A good agreement between experimental data (EXFOR) and the calculated cross-sections using two component exciton model with optical model for collision probabilities (Preeqmode 3) has been found. It is also found that the pre-equilibrium contribution dominates in these (n,p) reactions.

The radiation damage database: Section on helium cross section

A radiation damage database with emphasis on spallation interactions is described. Currently, the database contains damage energy, displacement, helium, and hydrogen cross sections for 23 elemental targets irradiated by proton and neutron projectiles up to 3.2GeV. In this paper, the focus is on proton-induced helium cross sections, but it is shown that for high energies (above about 500MeV) proton- and neutron-induced helium cross sections are almost equal. The cross section calculations were run on the Cascade–Exciton Model code (no options) and also on the Bertini code with three nuclear level-density models and multistage pre-equilibrium model on and off. Calculation and experimental results are compared. For various targets, we tried to determine which code and options give best agreement with experiment. In some cases, such determinations are uncertain, partly because of limited and conflicting experimental information and partly perhaps because of the need for modifications in the codes.

Influence of parity-dependence in the nuclear level density on the prediction of astrophysical reaction rates

A simple description for obtaining the parity distribution of nuclear levels in the pf + g 9 2 shell as a function of excitation energy was recently derived. We implement this in a global nuclear level density model. In the framework of the statistical model, cross sections and astrophysical reaction rates are calculated in the Fe region and compared to rates obtained with the common assumption of an equal distribution of parities. We find considerable differences, especially for reactions involving particles in the exit channel.

Possibilities of updating pu fast keutron cross sections with a theoretical analysis

Abstract Complete lack of experimental data on (n, xn)-reaction for Pu isotopes has stimulated the development of theoretical models for evaluation of nuclear data. The models employed include the coupled-channel method, multistep statistical model, precompound emission model, superfluid nuclear level density model involving collective effects. As an example, the neutron cross sections of 238-244Pu are analysed. The fission cross section data as well as the data on σnxn, σnn and neutron spectra can be correlated fairly well if collective, shell and deformation effects in neutron and fission channels are taken into account.

Odd-even effect in the nuclear level density and superfluid model of nuclei

The superfluid model of nuclei as worked out by Belyaev is used to account for the observed variation of the nuclear level density amongst odd, odd-mass and even nuclei.