Calculation Of Reaction Cross Sections Research Articles

Analysis of uncertainties inα-particle optical-potential assessment below the Coulomb barrier

Background: Recent high-precision measurements of alpha-induced reaction data below the Coulomb barrier have pointed out questions of the alpha-particle optical-model potential (OMP) which are yet open within various mass ranges. Purpose: The applicability of a previous optical potential and eventual uncertainties and/or systematic errors of the OMP assessment at low energies can be further considered on this basis. Method: Nuclear model parameters based on the analysis of recent independent data, particularly gamma-ray strength functions, have been involved within statistical model calculation of the (alpha,x) reaction cross sections. Results: The above-mentioned potential provides a consistent description of the recent alpha-induced reaction data with no empirical rescaling factors of the and/or nucleon widths. Conclusions: A suitable assessment of alpha-particle optical potential below the Coulomb barrier should involve the statistical-model parameters beyond this potential on the basis of a former analysis of independent data.

Cross Section Calculations of (n,2n) and (n,p) Nuclear Reactions on Germanium Isotopes at 14–15 MeV

Neutron incident reaction cross sections of Germanium isotopes (70,72,74,76Ge) were investigated for the (n,2n) and (n,p) reactions around 14–15 MeV. Cross section calculations have been presented for 70Ge(n,2n)69Ge, 72Ge(n,2n)71Ge, 74Ge(n,2n)73Ge, 76Ge(n,2n)75Ge, 70Ge(n,p)70Ga, 72Ge(n,p)72Ga, 74Ge(n,p)74Ga, and 76Ge(n,p)76Ga reactions. Theoretical calculations were performed with four different computer codes: ALICE/ASH for the Geometry Dependent Hybrid model, TALYS 1.6 for two component Exciton model, EMPIRE 3.2 Malta for Exciton model and PCROSS for Full Exciton model with the incident neutron energy up to 20 MeV. The (n,2n) and (n,p) reaction cross section calculations were compared with empirical formulas derived by several researchers and compared with the experimental data obtained from EXFOR database as well as with evaluated Nuclear data files (ENDF/B-VII.1: USA 2014). Results show good agreement between the theoretical calculations having a major importance in nuclear data evaluation calculations and the experimental data from literature.

Reaction Cross Section Calculations in Neutron Induced Reactions and GEANT4 Simulation of Hadronic Interactions for the Reactor Moderator Material BeO

BeO is one of the most common moderator material for neutron moderation; due to its high density, neutron capture cross section and physical-chemical properties that provides usage at elevated temperatures. As it’s known, for various applications in the field of reactor design and neutron capture, reaction cross–section data are required. The cross–sections of (n,α), (n,2n), (n,t), (n,EL) and (n,TOT) reactions for 9 Be and 16 O nuclei have been calculated by using TALYS 1.6 Two Component Exciton model and EMPIRE 3.2 Exciton model in this study. Hadronic interactions of low energetic neutrons and generated isotopes–particles have been investigated for a situation in which BeO was used as a neutron moderator by using GEANT4, which is a powerful simulation software. In addition, energy deposition along BeO material has been obtained. Results from performed calculations were compared with the experimental nuclear reaction data exist in EXFOR.

Reaction Cross Section Calculations in Neutron Induced Reactions and GEANT4 Simulation of Hadronic Interactions for the Reactor Moderator Material BeO

Reaction Cross Section Calculations in Neutron Induced Reactions and GEANT4 Simulation of Hadronic Interactions for the Reactor Moderator Material BeO

Reaction Cross Section Calculations in Neutron Induced Reactions and GEANT4 Simulation of Hadronic Interactions for the Reactor Moderator Material BeO

Reaction Cross Section Calculations in Neutron Induced Reactions and GEANT4 Simulation of Hadronic Interactions for the Reactor Moderator Material BeO

Partial cross sections of theMo92(p,γ)reaction and theγstrength inTc93

Background: Mo92 is the most abundant nucleus of the p nuclei, with an isotopic abundance of more than 14 %. The γ-process nucleosynthesis is believed to produce Mo92 but fails to explain its large abundance, especially with respect to the other p nuclei produced in the same stellar environment. Further studies require precise nuclear models for the calculation of reaction cross sections. Purpose: A measurement of the total and partial cross sections of the Mo92(p,γ)Tc93 reaction allows for a stringent test of statistical-model predictions. Not only different proton+nucleus optical model potentials, but also the γ-ray strength function of Tc93 can be investigated. In addition, high-resolution in-beam γ-ray spectroscopy enables the determination of new precise nuclear structure data for Tc93. Method: Total and partial cross-section values were measured by using the in-beam method. Prompt γ rays emitted during the irradiation of Mo92 with protons at seven different energies between 3.7 and 5.3 MeV were detected by using the high-purity germanium (HPGe) detector array HORUS at the Institute for Nuclear Physics, University of Cologne. The γγ-coincidence method was applied to correlate γ-ray cascades in Tc93 with their origin in the Mo92+p compound state. Results: The measured cross sections are compared to Hauser-Feshbach calculations by using the statistical-model code talys on the basis of different nuclear physics input models. Using default settings based on standard phenomenological models, the experimental values cannot be reproduced. A shell-model calculation was carried out to predict the low-energy M1 strength in Tc93. Together with Gogny-Hartree-Fock-Bogoliubov (Gogny-HFB) or Skyrme-HFB plus quasi-particle random-phase approximation (QRPA) models for the γ-ray strength function, the agreement between experimental data and theoretical predictions could be significantly improved. In addition, deviations from the adopted level scheme were found. Conclusions: By using Gogny- or Skyrme-HFB+QRPA E1 and shell-model M1 strength functions, statistical-model predictions can be significantly improved. Partial cross sections provide a valuable testing ground for γ-ray strength functions for nuclear astrophysics applications. In addition, they can be used to investigate nuclear-structure properties of the compound nucleus.

English

The simple local optical potential adopted in analyzing successfully elastic scattering data in the delta resonance region has been emphasized here. This is based on obtaining the same nature for the potential by extracting potential points from available  phase shifts at 114, 163, 240 and 340 MeV using inverse scattering theory within the framework of Klein-Gordon equation.  Luckily, and as expected, the obtained analytical potential form has also been used successfully in accounting for the experimental angular distributions at another nearby four energies, namely 170, 220, 230, and 270 MeV. At energies considered herein, the calculated reaction cross sections are in good agreement with available experimental ones, and are in spectral match with experimental ones. The nature of the real part of the potential showed a change from attractive to repulsive at about 200 MeV, and the imaginary part is dominated by the surface absorption term. In treating the pion-nucleus scattering problem, we found that there is no privacy for a doubly closed-shell self-conjugate target nucleus compared to another nucleus, at least  light bound nucleus, and for incident pion energies in the domain of the delta resonance region. Instead, it seems that the description of the scattering process is mainly attributed to the geometrical structure of the target nucleus. This is a first time corollary, and more investigations are needed. Key words: Pion-nucleus potential, elastic scattering, inverse scattering theory, high energy physics.

Analyses of alpha–alpha elastic scattering data in the energy range 53.4–119.9 MeV

The differential and reaction cross sections for alpha–alpha elastic scattering at energies ranging from 50 to 120 MeV (lab. system) have been clearly explained for the first time, by using a new optical potential type. This potential, which is different from all other proposed potentials, is composed of two real parts: one is an attractive squared Woods–Saxon and the other is a repulsive core of the Woods–Saxon form in addition to a surface Woods–Saxon form for the imaginary part. The nature of the real part has been determined from available phase shifts through using inverse scattering theory for the identical particles at a fixed energy, adopting the framework of the Schrödinger equation. It is found that the repulsive real part is essential for improving the fit to the measured elastic differential cross sections, and in explaining the kink that appears at r < 1.0 fm in the shape of the real part of the potential. Using this new potential, our calculated reaction cross sections are in reasonable agreement with the ones reported by both Darriulat et al. (Phys. Rev. 137, B315 (1965). doi:10.1103/PhysRev.137.B315) and Brown and Tang (Nucl. Phys. A, 170, 225 (1971). doi:10.1016/0375-9474(71)90633-6 ).

Complete Glauber calculations of reaction and interaction cross sections for light-ion collisions

The differences of the interaction and reaction cross sections for collisions between relativistic light ions of mass number in the range of A < 40 are calculated on the basis of Glauber theory. In the optical approximation of Glauber theory, these differences are about 1% of the interaction cross sections. Upon taking into account all diagrams in Glauber theory, these differences reach 3 to 4% of the interaction cross section.

Calculation of Reaction Cross Sections for Producing Br-75 in the Energy Range of 5-40 MeV

Calculation of Reaction Cross Sections for Producing Br-75 in the Energy Range of 5-40 MeV

Comparison of Level Density Models for the 60,61,62,64Ni(p, n) Reactions of Structural Fusion Material Nickel from Threshold to 30 MeV

The knowledge of level density for reaction cross-section calculations are needed for various applications such as fission and fusion reactor design, accelerator driven sub-critical systems, nuclear medicine, neutron capture and astrophysics. In this study, the excitation functions for (p, n) reactions from reaction threshold to 30 MeV proton incident energy on 60Ni, 61Ni, 62Ni and 64Ni isotopes were calculated using TALYS 1.6 nuclear code involving the level density models. This is of importance to the validation of nuclear model approaches with increased predictive power. There are several models of level density that can be used to predict cross-section. In this work, the (p, n) cross-sections would be calculated using three different model of level density, such as constant temperature model, back-shifted fermi gas model and generalized superfluid model on 60,61,62,64Ni reactions. The (p, n) reaction cross-section calculations for 60,61,62,64Ni target nuclei were compared with each other and the experimental nuclear reaction data obtained from EXFOR database.

Calculation of photo-nuclear reaction cross sections for16O

Because of the high thermal expansion coefficient of uranium, the fuel used in nuclear power plants is usually in the form of UO2 which has ceramic structure and small thermal expansion coefficient. UO2 include one uranium atom and two oxygen atoms. After fission progress, total energy values of emitted gamma are about 14 MeV. This gamma energy may cause transmutation of 16 O isotopes. Transmutation of 16 O isotopes changes physical properties of nuclear fuel. Due to above explanations, it is very important to calculate photo-nuclear reaction cross sections of 16 O. In this study; for (γ,p), (γ,np), (γ,n) and (γ,2n) reactions of 16 O, photo-nuclear reaction cross-sections were calculated using different models for pre-equilibrium and equilibrium effects. Taking incident gamma energy values up to 40 MeV, Hybrid and Cascade Exciton Models were used for pre-equilibrium calculations and Weisskopf-Ewing (Equilibrium) Model was used for equilibrium model calculations. Calculation results were compared with experimental and theoretical data. While experimental results were obtained from EXFOR, TENDL-2013, JENDL/PD-2004 and ENDF/B VII.1 data base were used to get theoretical results.

(γ, 2n)-Reaction cross-section calculations of several even-even lanthanide nuclei using different level density models

There are several level density models that can be used to predict photo-neutron cross sections. Some of them are Constant Temperature + Fermi Gas Model (CTFGM), Back-Shifted Fermi Gas Model (BSFM), Generalized Superfluid Model (GSM), Hartree-Fock-Bogoliubov microscopic Model (HFBM). In this study, the theoretical photo-neutron cross sections produced by (γ, 2n) reactions for several eveneven lanthanide nuclei such as 140,142Ce, 142,144,146,148,150Nd, 144,148,150,152,154Sm, and 160Gd have been calculated on the different level density models as mentioned above by using TALYS 1.6 and EMPIRE 3.1 computer codes for incident photon energies up to 30 MeV. The obtained results have been compared with each other and available experimental data existing in the EXFOR database. Generally, at least one level density model cross-section calculations are in agreement with the experimental results for all reactions except 144Sm(γ, 2n)142Sm along the incident photon energy, TALYS 1.6 BSFM option for the level density model cross-section calculations can be chosen if the experimental data are not available or are improbable to be produced due to the experimental difficulty.

(γ, 2n)-Reaction Cross-Section Calculations of Several Even–Even Lanthanide Nuclei Using Different Level Density Models

(γ, 2n)-Reaction Cross-Section Calculations of Several Even–Even Lanthanide Nuclei Using Different Level Density Models

Reaction Cross-Section, Stopping Power and Penetrating Distance Calculations for the Structural Fusion Material 54Fe in Different Reactions

Nuclear reaction codes give us simplicity to investigate phenomena of nuclear physics. There have many computer programs such as TALYS, EMPIRE, ALICE/ASH, PCROSS, FLUKA and GEANT4. The stopping power of alpha, deuteron, proton and triton in 54Fe materials is acquired as it has helpful applications of shielding and choosing the proper thickness of the target. Level density is very important to understanding nuclear reaction mechanism. The knowledge of level density for reaction cross-section calculations are required for various application such as astrophysics, accelerator driven sub-critical systems, nuclear medicine, fission and fusion reactor design and neutron capture. In this study, we calculated the cross-sections of 54Fe using TALYS 1.6 and EMPIRE 3.1 codes for different reactions through the four level density models. Stopping powers and penetrating distances were calculated for the alpha, deuteron, proton and triton particles, taking into consideration all possible reactions in 54Fe for incident energies of 1–45 MeV using GEANT4 calculation code. The obtained reaction cross-section results have been compared with the each other and against the experimental nuclear reaction data existing in EXFOR database.

(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.

Intermediate-energy four-body breakup calculations forC22

The heaviest particle-bound carbon isotope, $^{22}\mathrm{C}$, is thought to have a Borromean three-body structure. We discuss and compare four-body, i.e. three-body projectile plus target, reaction model calculations of reaction cross sections for such systems that use the fast adiabatic approximation. These methods are efficient and well-suited for quantitative analyses of reactions of neutron-rich nuclei with light target nuclei at secondary beam energies of $\ensuremath{\approx}300$ MeV/nucleon, as are now becoming available. We compare the predictions of the adiabatic model of the reaction both without and when including the additional eikonal approximation that has been used extensively. We show that the reaction cross section calculations have only limited sensitivity to the size and structure of $^{22}\mathrm{C}$ and that the differences arising from use of the eikonal approximation of the reaction mechanism are of a similar magnitude.

Prompt fission neutron emission calculations and description of sub-barrier fission cross section resonances for 234U()

Abstract Prompt emission quantities of 234U( n , f ) (average quantities as a function of fragment mass, average quantities as a function of total kinetic energy (TKE) and total average quantities) have been calculated within the Point-by-Point model. The recently measured fission fragment distributions at incident energies (En) ranging from 0.2 MeV to 5 MeV have been used. The insensibility of the fragment pair multiplicity ν pair to the partition of total excitation energy (TXE) between complementary fully accelerated fission fragments has been confirmed. This gives confidence in the predicted total average prompt emission data as a function of En and of average quantities as a function of TKE at different incident energies of 234U( n , f ). The systematic behavior of experimental ratios ν H / ν pair as a function of heavy fragment mass number A H together with the TXE partition based on modeling at scission allow the parameterization of the excitation energy ratio E H ⁎ / TXE . This opens up the possibility to provide ν ( A ) of 234U in the absence of any experimental data. For the first time the calculation of 〈 ν 〉 ( TKE ) at many En revealed two interesting aspects: the slope d TKE / d ν does not vary with En and the flattening of 〈 ν 〉 at low TKE values is more pronounced at low incident energies. The correlation between the sub-barrier resonant behavior of the fission cross section of fertile actinides (characterizing the pre-scission stage) and the visible fluctuations of their fission fragment and prompt neutron emission data (characterizing the post-scission stage), already discussed in the case of 238U( n , f ) is outlined and quantitatively supported by 234U( n , f ), too. The pronounced vibrational resonances in the experimental fission cross section of 234U placed below 1 MeV can be described by the statistical model for reaction cross section calculation including the optical model for fission.

(p,α) Reaction Cross Sections Calculations of Fe and Ni Target Nuclei Using New Developed Semi-empirical Formula

Iron (Fe) and nickel (Ni) are important fusion structural materials in reactor technology. The gas production in the metallic structure arising from many different types of nuclear reactions has been a significant damage mechanism in structural components of fusion reactors. The hydrogen and its isotopes at high temperatures leave out of the metallic lattice but the alpha (α) particles that remain in the lattice generate helium (He) gas bubbles. In other words, the α particles can cause serious changes in the physical and mechanical properties of the fusion structural materials. In this study, the excitation functions of 54,57Fe(p,α) and 58,60,61,64Ni(p,α) reactions have been investigated in the incident proton energy range of 10–40 MeV to estimate the radiation damage effects on fusion structural materials used in the construction of the first walls and core of the reactor. The calculations of (p,α) reaction cross sections on 54,57Fe and 58,60,61,64Ni have been made by using PCROSS code and CEM95 code. The full exciton and cascade exciton model (CEM95) for pre-equilibrium calculations and Weisskopf-Ewing model for equilibrium calculations are used. Besides, the semi-empirical cross section formula with new coefficient obtained by Tel et al. (Pramana J Phys 74:931–943, 2010) has been applied for (p,α) reactions at 17.9 MeV proton incident energy.

Electron pair emission from W(110): Response to a spin-polarized surface state

Details of a spin-polarized surface state on W(110) with a Dirac-cone-like dispersion are revealed by calculations of the spin- and layer-resolved density of states. After collisions of spin-polarized low-energy electrons, which impinge on the surface, with the surface-state electrons, correlated electron pairs are emitted, which have either parallel or antiparallel spins. Calculations of the corresponding reaction cross sections demonstrate, first, a spin-resolved mapping of the surface-state dispersion with surface-parallel momentum. Second, momentum distributions of the outgoing electron pairs with parallel and antiparallel spins allow a separation of Coulomb correlation and exchange effects.