Pre-equilibrium Nuclear Reactions Research Articles

A Comparison Between the Theoretical Cross Section Based on the Partial Level Density Formulae Calculated by the Exciton Model with the Experimental Data for (_79^197)Au nucleus

In this paper, the theoretical cross section in pre-equilibrium nuclear reaction has been studied for the reaction at energy 22.4 MeV. Ericson’s formula of partial level density PLD and their corrections (William’s correction and spin correction) have been substituted in the theoretical cross section and compared with the experimental data for nucleus. It has been found that the theoretical cross section with one-component PLD from Ericson’s formula when doesn’t agree with the experimental value and when . There is little agreement only at the high value of energy range with the experimental cross section. The theoretical cross section that depends on the one-component William's formula and on-component corrected to spin PLD formula doesn't agree with the experimental cross section. But in case of theoretical cross section based on two-component Ericson's and William's PLD formulae it has been found that there is acceptable agreement when the exciton number is taken .

Investigation of Isospin Conservation Effects on Pre-Equilibrium Nuclear Reactions for Some Nuclei

The pre-equilibrium emission spectra have been studied and calculated using the exciton model. The calculations took different reactions (nucleon – nucleon, nucleon – cluster, cluster – nucleon) at low and high incident energies to investigate and study the influence of adding the isospin conservation effects into the nuclear level density on the energy spectra. The isospin conservation effect added to the state density showed no significance variation for mixed and conserved isospin calculations for all reactions at different incident energies. The results were obtained by depending on the PRECO-2006 code of C. Kalbach.

Calculated differential and double differential cross section of DT neutron induced reactions on natural chromium (Cr)

Chromium is an important alloying element of stainless steel (SS) and SS is the main constituent of structural material proposed for fusion reactors. Energy and double differential cross section data will be required to estimate nuclear responses in the materials used in fusion reactors. There are no experimental data of energy and double differential cross section, available for neutron induced reactions on natural chromium at 14 MeV neutron energy. In this study, energy and double differential cross section data of (n,p) and (n,α) reactions for all the stable isotopes of chromium have been estimated, using appropriate nuclear models in TALYS code. The cross section data of stable isotopes are later converted into the energy and double differential cross section data of natural Cr using the isotopic abundance. The contribution from compound, pre-equilibrium and direct nuclear reaction to total reaction have also been calculated for 52,50Cr(n,p) and 52Cr(n,α). The calculation of energy differential cross section shows that most of emitted protons and alpha particles are of 3 and 8 MeV respectively. The calculated data is compared with the data from EXFOR data library and is found to be in good agreement.

Reaction cross section calculation of some alkaline earth elements

Reaction cross section knowledge is crucial to application nuclear physics such as medical imaging, radiation shielding and material evaluations. Nuclear reaction codes can be used if the experimental data are unavailable or are improbably to be produced because of the experimental trouble. In this study, there action cross sections of some target alkaline earth elements have been calculated by using pre-equilibrium and equilibrium nuclear reaction models for nucleon induced reactions. While these calculations, the Hybrid Model, the Geometry Dependent Hybrid Model, the Full Exciton Model, the Cascade Exciton Model for pre-equilibrium reactions and the Weisskopf-Ewing Model for equilibrium reactions have been used. The calculated cross sections have been discussed and compared with the experimental data taken from Experimental Nuclear Reaction Data library.

Studying the Nuclear Structure of Some Target Nuclei Used for Radiotherapy Nuclei Production by Using Skyrme-Hartree-Fock Method

The nuclear structure for some target nuclei namely: 32S, 58Ni, 89Y, 90Zr, 100Mo and 197Au used for production of the therapeutic radionuclides; 32P, 58Co, 89Sr, 90Y, 99Mo, 100Tc, 197Pt and 197Hg has been investigated using Skyrme-Hartree-Fock method based on Skyrme effective two-body interaction. For these purpose, we have calculated the various nuclear densities, the corresponding root mean square radii and nuclear binding energies. The density dependent initial neutron and proton exciton numbers have been also calculated which give the ability to investigate the neutron and proton induced reaction cross-sections for these target nuclei using hybrid model for pre-equilibrium nuclear reactions. The calculated results are compared with available experimental data.

Investigation of the production of 68Ga using pre-equilibrium models

In this study, some nuclear reactions for the production of 68Ga radioisotope are investigated using pre-equilibrium nuclear reaction models. For this aim, by the pre-equilibrium reaction mechanisms, the excitation functions and emission spectra of some nuclear reactions for the production of 68Ga radioisotope are calculated. These calculations are performed in the ALICE/ASH and the TALYS 1.6 codes. The obtained results have been discussed and compared with the available experimental results.

Calculation of excitation functions of the 5 4 , 5 6 , 5 7 , 5 8 Fe(p, n) reaction from threshold to 30 MeV

The cross-sections for the formation of 54,56,57,58Co in the 54,56,57,58Fe(p, n) reaction from threshold to 30 MeV protons have been theoretically calculated using the TALYS-1.4 nuclear model code, whereby we have studied major nuclear reaction mechanisms, including direct, pre-equilibrium and compound nuclear reaction. Subsequently, the level density and shell damping parameters have been adjusted and at the same time, the odd–even effects are well comprehended. The excitation functions have been compared with experimental nuclear data. It is observed that the theoretical cross-sections match fairly well. Proton-induced reaction cross-sections provide clues to understand the nuclear structure and offers a good testing ground for ideas about nuclear forces. In addition, complete information in this field is very much required for application in accelerator-driven subcritical system.

(3He,xn) Reaction Cross-Section Calculations for the Structural Fusion Material 181Ta in the Energy Range of 14–75 MeV

The theoretical neutron-production cross-sections produced by 181Ta(3He,xn)184−xRe reactions (x = 1–7) for structural fusion material 181Ta in 3He-induced reactions have been performed in the incident 3He energy range of 14–75 MeV. Reaction cross-sections, based on theoretical pre-equilibrium nuclear reaction models, have been calculated theoretically by means of the TALYS 1.6 two component exciton, EMPIRE 3.1 exciton, ALICE/ASH geometry dependent hybrid (GDH) and ALICE/ASH hybrid models. The neutron-production cross-section results of the models have been compared with the each other and against the experimental nuclear reaction data (EXFOR). Except the 181Ta(3He,2n)182Re and 181Ta(3He,7n)177Re reactions, the ALICE/ASH cross-section calculations show generally agreement with the experimental values for all reactions used in this study. The ALICE/ASH–GDH model can be suggested, if the experimental data are unavailable or are improbably to be produced because of the experimental troubles.

Nuclear interaction dynamics in the 56Fe (α, xn) reaction

Neutron spectra and angular distributions in the 56Fe (α, xn) reaction are measured at α-particle energies of 12.5, 16.3, 18.3, 26.8, and 45.2 MeV. The measurements are performed using time-of-flight fast neutron spectrometers on pulsed accelerators. The measured data are analyzed in the context of equilibrium, preequilibrium, and direct nuclear reaction mechanisms. The contributions from equilibrium, preequilibrium, and direct mechanisms of neutron emission are studied over a wide range of α-particle energies.

Pre-equilibrium neutron-emission spectra of 238U with an effective nucleon–nucleon interactions

In this study, the initial exciton numbers for the target nucleus 238U were calculated through a new method offered by Tel et al. (Ann. Nucl. Energy, 35, 220, 2008). Neutron-emission spectra produced by (n,xn) reactions on 238U nuclei have been calculated by using Hartree–Fock method with effective nucleon–nucleon Skyrme interactions with SKM∗ parameters. Pre-equilibrium nuclear reactions have been used to investigate the effect of initial exciton numbers on the nucleon emission spectra. Calculations have been made in the framework of the hybrid, equilibrium and GDH models using ALICE/ASH computer code. The initial exciton numbers calculated with the theoretical neutron and proton densities have been obtained with SKM∗ for the 238U(n,xn) reaction at 14.0 and 18.0MeV incident neutron energies. We also compared the geometry-dependent hybrid model (GDH), newly evaluated with the initial exciton number calculations of the neutron emission spectra of the 238U(n,xn) reaction. The obtained results are discussed and compared with the available experimental data and are shown to be in agreement with each other. All calculated results have been compared with experimental data from Experimental Nuclear Reaction Data (EXFOR).

Pre-equilibrium Emission Spectra Calculations of 232Th(n,xn) Using New Evaluated Method

The knowledge of the thorium (232Th) cycle potentialities are required for the design of a fusion-fission (hybrid) reactor. Pre-equilibrium nuclear reactions have been used to investigate the effect of initial exciton numbers on the nucleon emission spectra. In this study, the initial exciton numbers for the target nucleus of 232Th were calculated through a method of offered by Tel et al. and then were used to obtain the effect cross section of the neutron emission spectra. Using this new method, a different way from the literature, the initial exciton numbers calculated with the theoretical neutron and proton densities have been obtained with SKM* on the 232Th(n,xn) reaction at 14.1 and 18.0 MeV incident neutron energies. The results were analyzed by comparing the empirical results in the literature.

Neutron skin effect of some Mo isotopes in pre-equilibrium reactions

The neutron skin effect has been investigated for even isotopes of molybdenum at 25.6 MeV 94 − 100Mo(p, xn) reaction using the geometry-dependent hybrid model of pre-equilibrium nuclear reactions. Here the initial neutron/proton exciton numbers were calculated from the neutron/ proton densities obtained from an effective nucleon–nucleon interaction of the Skyrme type. Initial exciton numbers from different radii of even Mo isotopes were used to obtain the corresponding neutron emission spectra. In this investigation the calculated results are compared with the experimental data as also with each other. The results using central densities in the geometry-dependent hybrid model are in better agreement with the experimental data.

The effect of the initial exciton numbers on 54,56Fe(p, xp) Pre-Equilibrium Reactions

In pre-equilibrium nuclear reactions, the geometry-dependent hybrid model is applied with the use of the neutron and proton densities to investigate the effect of initial exciton numbers on the nucleon emission spectra. The initial exciton numbers calculated with the theoretical neutron and proton densities have been obtained within the Skryme-Hartree-Fock method with SKM* and SLy4 forces on target nuclei in the 54,56Fe(p, xp) reaction at 61.5-MeV incident proton energy by using a new calculationmethod of Tel et al. Also, the differences between the initial exciton numbers for protons and neutrons as a function of nuclear radius, focusing on systematic discrepancies correlated to differences in the proton and neutron densities have been investigated.

PHASE-OTI: A pre-equilibrium model code for nuclear reactions calculations

The present work focuses on a pre-equilibrium nuclear reaction code (based on the one, two and infinity hypothesis of pre-equilibrium nuclear reactions). In the PHASE-OTI code, pre-equilibrium decays are assumed to be single nucleon emissions, and the statistical probabilities come from the independence of nuclei decay. The code has proved to be a good tool to provide predictions of energy-differential cross sections. The probability of emission was calculated statistically using bases of hybrid model and exciton model. However, more precise depletion factors were used in the calculations. The present calculations were restricted to nucleon–nucleon interactions and one nucleon emission. Program summary Program title: PHASE-OTI Catalogue identifier: AEDN_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEDN_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 5858 No. of bytes in distributed program, including test data, etc.: 149 405 Distribution format: tar.gz Programming language: Fortran 77 Computer: Pentium 4 and Centrino Duo Operating system: MS Windows RAM: 128 MB Classification: 17.12 Nature of problem: Calculation of the differential cross section for nucleon induced nuclear reaction in the framework of pre-equilibrium emission model. Solution method: Single neutron emission was treated by assuming occurrence of the reaction in successive steps. Each step is called phase because of the phase transition nature of the theory. The probability of emission was calculated statistically using bases of hybrid model [1] and exciton model [2]. However, more precise depletion factor was used in the calculations. Exciton configuration used in the code is that described in earlier work [3]. Restrictions: The program is restricted to single nucleon emission and nucleon–nucleon interactions. Running time: 5–30 minutes

Calculation of induced reactions of 3He-particles on natSb in 10–34 MeV energy range

Calculations for the excitation functions of the 121Sb( 3He, xn) 121,122,123I, and 123Sb( 3He xn) 122,123,124,125I reactions have been carried out using statistical and pre-equilibrium nuclear reaction models in 10−34 MeV energy range. These excitation functions have been used to derive the excitation functions of the natSb( 3He, xn) 121,123,124I reactions and compared with reported measurements. For studying the improvement with measurements two values of the diffuseness parameter a w equal to 0.9 and 0.7 fm have been used in the calculations. The dependence of pre-equilibrium calculations on the initial exciton numbers has also been considered.

New calculation of excitation functions of proton-induced reactions in some medical isotopes of Cu, Zn and Ga

The new calculations on the excitation functions of 61Ni(p,n) 61Cu, 62Ni(p,n) 62Cu, 64Ni(p,n) 64Cu, 63Cu(p,2n) 62Zn, 63Cu(p,n) 63Zn, 65Cu(p,n) 65Zn, 66Zn(p,n) 66Ga, 67Zn(p,2n) 66Ga, 67Zn(p,n) 67Ga and 68Zn(p,n) 68Ga reactions have been carried out in the 5–30 MeV proton energy range. The calculations involve the cascade exciton model, preequilibrium nuclear reaction model and exciton model. The calculated results are compared with the experimental data taken from the literature.

Evidence of shell effects in the excitation function of0.136‐MeVisomeric state populated in theNb93(n,2n)Nbm92reaction

Calculation for the excitation function of $0.136\text{\penalty1000-\hskip0pt}\mathrm{MeV}$ $({2}^{+})$ isomeric state in $^{92}\mathrm{Nb}$ has been carried out using Hauser-Feshbach and pre-equilibrium nuclear reaction models in $10--20\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ energy range. A satisfactory agreement between the calculation and measurements requires the suppression of contribution from the negative-parity doublet consisting of the $0.226\text{\penalty1000-\hskip0pt}\mathrm{MeV}$ $({2}^{\ensuremath{-}})$ and $0.390\text{\penalty1000-\hskip0pt}\mathrm{MeV}$ $({3}^{\ensuremath{-}})$ states in $^{92}\mathrm{Nb}$. This can be explained on the basis of highly retarded gamma transitions of higher energy states to the negative-parity doublet on account of its different shell model configuration compared to the shell model configuration of positive-parity states.

NWY Model Calculations for Nucleon-Induced Multistep Direct Reactions

Calculations of the preequilibrium process are performed with the theory of Nishioka, Weidenmüller, and Yoshida (NWY), which is a quantum mechanical approach to the preequilibrium nuclear reactions. For a one-step process, cross sections given by the NWY theory are sum of DWBA cross sections which excite various lp-lh states, and those are averaged over the residual state weighted by the final states density. A true level density which is based on a random matrix model is used for this. A comparison of the calculated NWY one-step process with the experimental data is shown. For a two-step process, the NWY theory adopts a “sudden approximation.” An example of the two-step cross section calculation is made for 208Pb(p, p’) reaction.

Measurement and analysis of neutron spectra from a thick Ta target bombarded by7.2AMeV16Oions

Energy distributions of emitted neutrons were measured for $7.2A\mathrm{MeV}$ ${}^{16}\mathrm{O}$ ions incident on a thick ${}^{181}\mathrm{Ta}$ target. Measurements were done at $0\ifmmode^\circ\else\textdegree\fi{},$ $30\ifmmode^\circ\else\textdegree\fi{},$ and $60\ifmmode^\circ\else\textdegree\fi{}$ with respect to the projectile direction using the proton recoil scintillation technique. Comparison with calculated results from equilibrium and preequilibrium (PEQ) nuclear reaction models suggests the emission of PEQ neutrons at this projectile energy. This model also implies that PEQ emissions take place only before any scattering between target and projectile nucleons start. The paper discusses the method for selecting the initial exciton configuration with the help of measured data, and the stage at which the PEQ process is completed.

Calculations for the excitation functions of 3–26 MeV proton reactions on 66Zn, 67Zn and 68Zn

Calculation of excitation functions of 66Zn(p,n) 66Ga, 66Zn(p,n+p) 65Zn, 66Zn(p,2n) 65Ga, 67Zn(p,2n) 66Ga, 68Zn(p,n) 68Ga, 68Zn(p,2n) 67Ga natZn(p, xn) 66Ga and natZn(p, xn) 67Ga reactions has been carried out using the statistical and pre-equilibrium nuclear reaction models in the 3–26 MeV energy range. The calculational results are compared with the reported measurements and evaluations.