Group cross sections calculations
Just a few methods have been developped to compute multigroup cross-sections from ENDF data. We have developped an original method in order to get accuracy and to reduce the number of discretization points in the same time; this is why we have tried to use polynomial integration. In this paper, we describe this method: in the first part, we recall some physical hypothesis generally used to solve the linear Boltzmann equation: that is the frame in which the numerical method has been developped. Polynomial methods are really powerfull only if discretization points are suitably chosen. This choice is explained in the next part of this paper. In conclusion, some numerical results are given to illustrate our method
Fission cross section calculations for Pa isotopes
Based on the recently measured cross-section values for the neutron-induced fission of 231Pa and our experience gained with other isotopes, new self consistent neutron cross section calculations for n+231Pa have been performed up to 30 MeV. The results are quite different to the existing evaluations, especially above the first chance fission threshold. (authors)
Methods for calculating anisotropic transfer cross sections
The Legendre moments of the group transfer cross section, which are widely used in the numerical solution of the transport calculation can be efficiently and accurately constructed from low-order (K = 1--2) successive partial range moments. This is convenient for the generation of group constants. In addition, a technique to obtain group-angle correlation transfer cross section without Legendre expansion is presented. (author)
How to calculate colourful cross sections efficiently
Gleisberg, Tanju; Krauss, Frank
2008-01-01
Different methods for the calculation of cross sections with many QCD particles are compared. To this end, CSW vertex rules, Berends-Giele recursion and Feynman-diagram based techniques are implemented as well as various methods for the treatment of colours and phase space integration. We find that typically there is only a small window of jet multiplicities, where the CSW technique has efficiencies comparable or better than both of the other two methods.
Calculation of cross sections for heavy isotopes
In the present work an integrated system of codes for basic neutron data evaluation were assembled and built. Complete evaluations for the isotopes 240Pu, 241Pu, 242Pu and 238Pu were performed. The following cross sections: total, elastic, radiative capture, fission, total inelastic, partial inelastic, (n,2n), (n,3n) and differential elastic were evaluated as well as the average number of neutrons per neutron-induced fission and the average elastic scattering cosine in the lab system.The data for the plutonium isotopes were incorporated into the German KEDAK file. A method was developed for calculating the energy distributions of the second and third secondary neutrons from the A(n,2n) and (n,3n) reactions in the framework of the compound nucleus theory, and utilizing the nuclear data of the nuclei A, A-1, A-2. This method was used to generate the 238U secondary neutron energy distributions in the incident neutron energy range of 6 to 15 MeV. A nuclear data evaluation for 237U in the resolved inelastic scattering range (10-700 keV) was performed. The compound elastic and partial inelastic scattering cross sections were used in the 238U secondary neutron energy distribution calculations. (B.G.)
Calculated medium energy fission cross sections
An analysis has been made of medium-energy nucleon induced fission of 238U and 237Np using detailed models of fission, based upon the Bohr-Wheeler formalism. Two principal motivations were associated with these calculations. The first was determination of barrier parameters for proton-rich uranium and neptunium isotopes normally not accessible in lower energy reactions. The second was examination of the consistency between (p,f) experimental data versus new (n,f) data that has recently become available. Additionally, preliminary investigations were also made concerning the effect of fission dynamics on calculated fission cross sections at higher energies where neutron emission times may be significantly less than those associated with fission
Electronic stopping cross sections for use in ion range calculation
Theoretical and empirical methods of determining the electronic stopping cross sections are discussed. The values used by various authors in ion range calculations are outlined. Recommendations are made for future range calculations. (author)
abo-cross: Hydrogen broadening cross-section calculator
Barklem, P. S.; Anstee, S. D.; O'Mara, B. J.
2015-07-01
Line broadening cross sections for the broadening of spectral lines by collisions with neutral hydrogen atoms have been tabulated by Anstee & O'Mara (1995), Barklem & O'Mara (1997) and Barklem, O'Mara & Ross (1998) for s-p, p-s, p-d, d-p, d-f and f-d transitions. abo-cross, written in Fortran, interpolates in these tabulations to make these data more accessible to the end user. This code can be incorporated into existing spectrum synthesis programs or used it in a stand-alone mode to compute line broadening cross sections for specific transitions.
Parametric equations for calculation of macroscopic cross sections
Botelho, Mario Hugo; Carvalho, Fernando, E-mail: mariobotelho@poli.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear
2015-07-01
Neutronic calculations of the core of a nuclear reactor is one thing necessary and important for the design and management of a nuclear reactor in order to prevent accidents and control the reactor efficiently as possible. To perform these calculations a library of nuclear data, including cross sections is required. Currently, to obtain a cross section computer codes are used, which require a large amount of processing time and computer memory. This paper proposes the calculation of macroscopic cross section through the development of parametric equations. The paper illustrates the proposal for the case of macroscopic cross sections of absorption (Σa), which was chosen due to its greater complexity among other cross sections. Parametric equations created enable, quick and dynamic way, the determination of absorption cross sections, enabling the use of them in calculations of reactors. The results show efficient when compared with the absorption cross sections obtained by the ALPHA 8.8.1 code. The differences between the cross sections are less than 2% for group 2 and less than 0.60% for group 1. (author)
Cross section probability tables in multi-group transport calculations
The use of cross section probability tables in multigroup transport calculations is presented. Emphasis is placed on how probability table parameters are generated in a multigroup cross section processor and how existing transport codes must be modifed to use them. In order to illustrate the accuracy obtained by using probability tables, results are presented for a variety of neutron and photon transport problems
Absolute cross-section of turbojet aviation engine calculation
Ryabokon, Evgen
2012-01-01
The calculation method of three-dimensional model of turbojet aviation engine is offered, thus the form of turbine vanes with spiralling is described like parametric surface. The method allows make the calculation of absolute cross-section (ACS) of turbojet aviation engines with different geometrical parameters. The calculation results of ACS of aviation engine are presented.
Cross section library based discrepancies in MCNP criticality calculations
In nuclear engineering several reactor physics problems can be approached using Monte Carlo neutron transport techniques, which usually give reliable results when properly used. The quality of the results is largely determined by the accuracy of the geometry model and the statistical uncertainty of the Monte Carlo calculation. There is, however, another potential source of error, namely the cross section data used with the Monte Carlo codes. It has been shown in several studies that there may be significant discrepancies between results calculated using cross section libraries based on different evaluated nuclear data files. These discrepancies are well known to the evaluators of nuclear data but less acknowledged by reactor physicists, who often rely on a single cross section library in their calculations. In this study, discrepancies originating from base nuclear data were investigated in a systematic manner using the MCNP4C code. Calculations on simplified UOX and MOX fuelled LWR lattices were carried out using cross section libraries based on ENDF/B-VI.8, JEFF-3.0, JENDL-3.3, JEF-2.2 and JENDL-3.2 evaluated data files. The neutron spectrum of the system was varied over a wide range by changing the ratio of hydrogen to heavy metal atoms. The essential isotopes underlying the discrepancies were identified and the roles of fission and absorption cross sections of the most important nuclides assessed. The results confirm that there are large systematic differences up to a few per cent in the multiplication factors of LWR lattices. The discrepancies are strongly dependent on material compositions and neutron spectra, and largely originate from U-238 and the primary fissile isotopes. It is concluded that these discrepancies should be taken into account in all reactor physics calculations, and that reactor physicists should not rely on results based on a single cross section library. (author)
Calculation of the intermediate energy activation cross section
Furihata, Shiori; Yoshizawa, Nobuaki [Mitsubishi Research Inst., Inc., Tokyo (Japan)
1997-03-01
We discussed the activation cross section in order to predict accurately the activation of soil around an accelerator with high energy and strong intensity beam. For the assessment of the accuracy of activation cross sections estimated by a numerical model, we compared the calculated cross section with various experimental data, for Si(p,x){sup 22}Na, Al(p,x){sup 22}Na, Fe(p,x){sup 22}Na, Si(p,x){sup 7}Be, O(p,x){sup 3}H, Al(p,x){sup 3}H and Si(p,x){sup 3}H reactions. We used three computational codes, i.e., quantum molecular dynamics (QMD) plus statistical decay model (SDM), HETC-3STEP and the semiempirical method developed by Silberberg et.al. It is observed that the codes are accurate above 1GeV, except for {sup 7}Be production. We also discussed the difference between the activation cross sections of proton- and neutron-induced reaction. For the incident energy at 40MeV, it is found that {sup 3}H production cross sections of neutron-induced reaction are ten times as large as those of proton-induced reaction. It is also observed that the choice of the activation cross sections seriously affects to the estimate of saturated radioactivity, if the maximum energy of neutron flux is below 100MeV. (author)
Measurement, calculation and evaluation of photon production cross-sections
The meeting proceedings were divided into three sessions devoted to the following topics: Experimental measurement and techniques (3 papers), calculation of photon cross-sections (9 papers), and evaluation (2 papers). A separate abstract was prepared for each of these papers. Refs, figs and tabs
Displacement cross section and DPA calculations using NMTC/JAERI
A new function calculating displacement cross sections using the Lindhard-Robinson model is implemented in the nucleon-meson transport code NMTC/JAERI. The nucleon-nucleus cross sections in the energy region above 950 MeV and the angular distribution data of elastic scattering are also modified to evaluate the displacement cross sections as accurate as possible. The displacement cross sections of Cr, Fe Ni, and type 316 stainless steel are calculated with the updated version of NMTC/JAERI. It is confirmed that the calculated displacement cross sections caused by the elastic scattering connect smoothly with the value of the JENDL PKA File at 20 MeV. With these calculation values, the displacement per atoms (DPA) in the beam window and target vessel of a mercury target are estimated in a framework of the neutronics design study of the spallation target bombarded with 1.5 GeV protons with a power of 5 MW. The following three beam conditions are selected in this calculation; (a) uniform distribution with average current density of 48 μA/cm2, (b) parabolic distribution with average current density of 48 μA/cm2, and (c) that with average current density of 24 μA/cm2. The DPAs are estimated as (a) 68, (b) 114, and (c) 70 DPA/yr at the beam windows, and (a) 41, (b) 52, and (c) 37 DPA/yr at the target vessel for the three cases, respectively. It is found that the DPAs obtained in this study are almost the same as the results of other design studies for spallation neutron source facilities. (author)
Calculation of 239Pu neutron inelastic cross sections
We have calculated cross sections for neutron-induced reactions on 239Pu between 0.001 and 5 MeV, with particular emphasis on inelastic scattering. Coupled-channel and Hauser-Feshbach statistical models were used. Within the coupled-channel calculations we employed neutron optical parameters derived from simultaneous fits to total, elastic, inelastic, and resonance data. The resulting transmission coefficients were used in Hauser-Feshbach statistical calculations having a fission channel based on a double-humped barrier representation. Barrier parameters and transition state enhancements needed to reproduce well the (n,f) cross sections between 0.001 and 5 MeV were in general agreement with those from other published analyses. Calculated compound-nucleus and direct-reaction components for inelastic scattering were combined incoherently, and the resultant cross sections agreed well with the Bruyeres-le-Chatel measurements for scattering from levels occupying the ground state rotational band. Our results are in substantial disagreement with ENDF/B-V values for these levels. We are presently performing DWBA calculations to determine direct-reaction components for states occupying higher-lying vibrational bands
Benchmark calculations of 150-group cross section library for LMR's
For the purpose of diversification of selection of cross section library for neutron calculation of LMR, the 150 multi-group cross section library was generated from ENDF-VI release. The set was then examined by analyzing measured reactivity quantities such as control rod worth, Doppler effect and sodium void effect for BFS critical assemblies that we obtained through the critical experiment plan for developing the KALIMER core design. The calculated results based on 9 group structure using the new set were also compared with those of JEF set based on the same group structure and compared with those of the same set based on 25 group structure to find the proper group structure. ENDF-VI-based set shows a small deviation in predicting measured integral quantities in comparison with the previous set and a small group effect
Calculation of light nucleus reaction cross sections in Geant4
Uzhinsky, V.
2012-01-01
Total reaction cross sections of light projectile nucleus (H-2, H-3, He-3 and He-4) interactions with nuclei are calculated using Geant4 models, and compared with experimental data. It is shown that the models give various predictions at low energies, in the region of the Coulomb barrier. "Shen model" (W.-Q. Shen et al., Nucl. Phys. {\\bf A491} (1989) 130) is identified as an improvement over other models.
Neutron cross section calculations for fission-product nuclei
To satisfy nuclear data requirements for fission-product nuclei, Hauser-Feshbach statistical calculations with preequilibrium corrections for neutron-induced reactions on isotopes of Se, Kr, Sr, Zr, Mo, Sn, Xe, and Ba between 0.001 and 20 MeV. Spherical neutron optical parameters were determined by simultaneous fits to resonance data and total cross sections. Isospin coefficients appearing in the optical potentials were determined through analysis of the behavior of s- and p-wave strengths as a function of mass for a given Z. Gamma-ray strength functions, determined through fits to stable-isotope capture data, were used in the calculation of capture cross sections and gamma-ray competition to particle emission. The resulting (n,γ), (n,n'), (n,2n), and (n,3n) cross sections, the secondary neutron emission spectra, and angular distributions calculated for 19 fission products will be averaged to provide a resulting ENDF-type fission-product neutronics file. 11 references
Coupled neutron and photon cross sections for transport calculations
A compact set of multigroup cross sections and transfer tables for use in neutron and photon transport calculations was prepared from ENDF/B-IV using the NJOY processing system. The library includes prompt and steady-state coupled sets for neutrons and photons in FIDO format, prompt and steady-state fission spectra (chi vectors) for the fissionable isotopes, and a table of useful response functions including heating and gas production. These multigroup constants should be useful for a wide variety of problems where self-shielding is not important. 15 references
Evaluation and calculation of neutron transactinide cross-sections
This paper reviews the state of the art of nuclear theory and its application to the evaluation and calculation of neutron reaction cross sections of transactinium isotopes. In particular, the paper describes the current evaluation of the total files of neutron reaction data for 240Pu and 241Pu in the energy range between 10-5 eV and 15 MeV based on a thorough analysis of available experimental data and on the use of modern theoretical concepts, and the work in progress on the evaluation of the total neutron reaction data file for 242Pu and 241Am. (author)
Simplified polynomial representation of cross sections for reactor calculation
It is shown a simplified representation of a cross section library generated by transport theory using the cell model of Wigner-Seitz for typical PWR fuel elements. The effect of burnup evolution through tables of reference cross sections and the effect of the variation of the reactor operation parameters considered by adjusted polynomials are presented. (M.C.K.)
A computer program for calculating effective capture cross section
FORTRAN program CPCS (Computer Program to analyze Capture TOF Spectra) was developed to deduce effective neutron capture cross sections from raw data obtained by a time-of-flight facility at the JAERI Electron Linear Accelerator. The data processing system for capture experiments consists of three stages, i.e. data acquisition, data handling (summing, listing, plotting, etc.), and data analysis (background determination, flux determination, normalization, etc.). In the three stages of processing, three respective computers are used; USC-3, FACOM U-200, and FACOM 230/75. CPCS is included in the stage of data analysis. A feature of this program is that the magnetic disk file is effectively used as INPUT/OUTPUT data storage interconnecting with other programs to determine neutron flux, to average calculated cross sections and to fit data with strength functions. This program is able to handle eight sets of TOF spectra with 8192 channels including channel block option simultaneously. Particular attention is paid to determine a precise background in the wide neutron energy range. (author)
Process of cross section generation for radiation shielding calculations, using the NJOY code
The process of multigroup cross sections generation for radiation shielding calculations, using the NJOY code, is explained. Photon production cross sections, processed by the GROUPR module, and photon interaction cross sections processed by the GAMINR are given. These data are compared with the data produced by the AMPX system and published data. (author)
Thanh Mai Vu; Takanori Kitada
2014-01-01
Recently, the researches on fast neutron spectrum system utilized thorium fuel are widely conducted. However, the recent thorium cross section libraries are limited compared to uranium cross section libraries. The impact of thorium cross section uncertainty on thorium fuel utilized accelerator driven system (ADS) reactivity calculation is estimated in this study. The uncertainty of the keff caused by 232Th capture cross section of JENDL-4.0 is about 1.3%. The uncertainty of JENDL-4.0 is neede...
A theoretical calculation of n-T scattering cross sections
By using the phase shift analysis method, the σt', σnn'. σnon and σ(θ) of n-T scattering were calculated. The calculated results are in good agreement with the new experimental data and better than the previous calculations
The level density parameters are determined to reproduce level structure and/or resonance level spacing of the nucleus. In the statistical compound nucleus model, cross sections to discrete levels decrease abruptly, and continuum level cross section increase strongly above the energy point where the continuum levels switched on. In the present study, for the nucleus which level scheme were well determined up to higher excitation energy more than 10 MeV, discrete level cross sections were calculated and summed up and compared with the cross section to the assumed continuum level corresponding to the discrete levels above several MeV excitation energy. Calculation of the (n, n') cross sections were made with CASTHY code of Moldauer model option using level density parameters determined with former method. It is shown that the assumed continuum cross section is fairly large compared with the summed up cross section. Origins of the discrepancy were discussed. (J.P.N.)
A Calculation of Direct Radiative Recombination Cross Sections and Rate Coefficients
XIA Hai-Ning; CHEN Chong-Yang; SHI Xi-Heng; QI Jing-Bo; WANG Yan-Sen
2003-01-01
We calculate direct radiative recombination cross sections and rate coefficients for Be-like O4+, Si10+ and Na-like Fe15+ using nonrelativistic dipole approximation. In order to incorporate the screening effect due to the inner-shell electrons in the calculation, we use the distorted wave method instead of pure Coulomb approximation with effective charge. The calculated cross sections and rate coefficients are in agreement with other theoretical calculations and the experimental data.
Thanh Mai Vu
2014-01-01
Full Text Available Recently, the researches on fast neutron spectrum system utilized thorium fuel are widely conducted. However, the recent thorium cross section libraries are limited compared to uranium cross section libraries. The impact of thorium cross section uncertainty on thorium fuel utilized accelerator driven system (ADS reactivity calculation is estimated in this study. The uncertainty of the keff caused by 232Th capture cross section of JENDL-4.0 is about 1.3%. The uncertainty of JENDL-4.0 is needed to be enhanced to provide more reliable results on reactivity calculation for the fast system. The impact of uncertainty of 232Th capture cross section of ENDF/B-VII is small (0.1%. Therefore, it will cause no significant impact of the thorium cross section library on the thorium utilized ADS design calculation.
Calculation and preliminary analysis of group cross sections for gadolinium and its isotopes
Evaluated nuclear data files ENDL 78 and ENDF/B-IV and the cross section generation code FEDGROUP-R were used to produce averaged group cross sections for group systems BNAB and THSIG for gadolinium and its isotopes. Different sets of group cross sections for gadolinium (due to different evaluated data files or different processing codes) were compared and significant differences analyzed. The group capture cross sections for the isotopes of gadolinium were compared with published data. The group cross sections data sets prepared are analyzed as to what extent they can meet the requirements of cell calculations for gadolinium-loaded fuel. Some group cross section tables and cross section plots are presented. (author)
Improved calculation of total cross section for pair production by relativistic heavy ions
Eby, P. B.
1989-01-01
A calculation of the total cross section for direct electron-positron pair production by heavy ions is described. It combines the use of the Weizsaecker-Williams method for low-energy transfers and existing calculations for high-energy transfers. Higher-order corrections to the total cross section are calculated based on the Weizsaecher-Williams method and existing results for pair production by photons.
MUXS: a code to generate multigroup cross sections for sputtering calculations
This report documents MUXS, a computer code to generate multigroup cross sections for charged particle transport problems. Cross sections generated by MUXS can be used in many multigroup transport codes, with minor modifications to these codes, to calculate sputtering yields, reflection coefficients, penetration distances, etc
Calculation of double differential cross sections for structural materials by PEGASUS code
The neutron induced neutron and proton emission double differential cross sections were calculated with PEGASUS code for Cr, Fe and Ni and their isotopes. Results are in fair agreement with experimental data for neutron energy near 14 MeV, confirming that PEGASUS may be applied successfully to produce the double differential cross section data for JENDL. (author)
Neutron elastic scattering cross section measurements have been going on for a long period at the Studsvik Van de Graaff laboratory. The cross sections of a range of elements have been investigated in the energy interval 1.5 to 8 MeV. The experimental data have been compared with cross sections calculated with the optical model when using a local nuclear potential
Applicability of the cross section adjustment method based on random sampling (RS) technique to burnup calculations is investigated. The cross section adjustment method is a technique for reduction of prediction uncertainties in reactor core analysis and has been widely applied to fast reactors. As a practical method, the cross section adjustment method based on RS technique is newly developed for application to light water reactors (LWRs). In this method, covariance among cross sections and neutronics parameters are statistically estimated by the RS technique and cross sections are adjusted without calculation of sensitivity coefficients of neutronics parameters, which are necessary in the conventional cross section adjustment method. Since sensitivity coefficients are not used, the RS-based method is expected to be practically applied to LWR core analysis, in which considerable computational costs are required for estimation of sensitivity coefficients. Through a simple pin-cell burnup calculation, applicability of the present method to burnup calculations is investigated. The calculation results indicate that the present method can adequately adjust cross sections including burnup characteristics. (author)
Singh, Suvam; Naghma, Rahla; Kaur, Jaspreet; Antony, Bobby
2016-07-01
The total and ionization cross sections for electron scattering by benzene, halobenzenes, toluene, aniline, and phenol are reported over a wide energy domain. The multi-scattering centre spherical complex optical potential method has been employed to find the total elastic and inelastic cross sections. The total ionization cross section is estimated from total inelastic cross section using the complex scattering potential-ionization contribution method. In the present article, the first theoretical calculations for electron impact total and ionization cross section have been performed for most of the targets having numerous practical applications. A reasonable agreement is obtained compared to existing experimental observations for all the targets reported here, especially for the total cross section.
Calculation of differential cross section for dielectronic recombination with one-electron uranium
Calculation of the differential cross section for the dielectronic recombination with one-electron uranium within the framework of QED is presented. The contribution of the QED corrections and the interfernce of the photon multipoles is investigated
Maxwellian-averaged Cross Section Calculated From CENDL-3.0
2002-01-01
For the propose of using in astrophysics the Maxwellian-averaged cross sections of neutron capture,fission, (n, p) and (n, α) reactions are calculated from the CENDL-3.0, and the temperature (kT)from 1
PEGASUS: a preequilibrium and multi-step evaporation code for neutron cross section calculation
The computer code PEGASUS was developed to calculate neutron-induced reaction cross sections on the basis of the closed form exciton model preequilibrium theory and the multi-step evaporation theory. The cross sections and emitted particle spectra are calculated for the compound elastic scattering, (n,γ), (n,n'), (n,p), (n,α), (n,d), (n,t), (n,3He), (n,2n), (n,n'p), (n,n'α), (n,n'd), (n,n't), (n,2p) and (n,3n) reactions. The double differential cross sections of emitted particles are also calculated. The calculated results are written on a magnetic disk in the ENDF format. Parameter files and/or systematics formulas are provided for level densities, mass excess, radiation widths and inverse cross sections so that the input data to the code are made minimum. (author)
KAPSIES: A program for the calculation of multi-step direct reaction cross sections
We present a program for the calculation of continuum cross sections, sepctra, angular distributions and analyzing powers according to various quantum-mechanical theories for statistical multi-step direct nuclear reactions. (orig.)
Cross sections for fuel depletion and radioisotope production calculations in TRIGA reactors
For TRIGA Reactors, the fuel depletion and isotopic inventory calculations, depends on the computer code and in the cross sections of some important actinides used. Among these we have U-235, U-238, Pu-239, Pu-240 and Pu-241. We choose ORIGEN2, a code with a good reputation in this kind of calculations, we observed the cross sections for these actinides in the libraries that we have (PWR's and BWR), the fission cross section for U-235 was about 50 barns. We used a PWR library and our results were not satisfactory, specially for standard elements. We decided to calculate cross sections more suitable for our reactor, for that purpose we simulate the standard and FLIP TRIGA cells with the transport code WIMS. We used the fuel average flux and COLAPS (a home made program), to generate suitable cross sections for ORIGEN2, by collapsing the WIMS library cross sections of these nuclides. For the radioisotope production studies using the Central Thimble, we simulate the A and B rings and used the A average flux to collapse cross sections. For these studies, the required nuclides sometimes are not present in WIMS library, for them we are planning to process the ENDF/B data, with NJOY system, and include the cross sections to WIMS library or to collapse them using the appropriate average-flux and the program COLAPS. (author)
Single event upset cross section calculation for secondary particles induced by proton using Geant4
Based on Monte-Carlo software Geant4, a model for calculating the proton single event upset (SEU) cross section of SRAM cell was presented. The secondary particles induced by protons were considered and effective sensitive regions were determined according to the range of the secondary particles. The single event upset and multiple bits upset (MBU) cross sections for protons with different energy were calculated. The results are in agreement with the theoretical and experimental data. (authors)
Absorbing-sphere model for calculating ion-ion recombination total cross sections.
Olson, R. E.
1972-01-01
An 'absorbing-sphere' model based on the Landau-Zener method is set up for calculating the upper limit thermal energy (300 K) reaction rate and the energy dependence of the total cross sections. The crucial parameter needed for the calculation is the electron detachment energy for the outer electron on the anion. It is found that the cross sections increase with decreasing electron detachment energy.
The Weisskopf–Ewing (WE) and Hauser–Feshbach (HF) theory are statistical methods, which are often used to calculate photonuclear cross sections for compound nucleus reactions. In our past work, WE methodology was presented and photonuclear reaction cross sections for nucleon emission were calculated using WE theory. Here, our previous results, which neglect pre-equilibrium emissions and do not include multiple particle emission, are compared to those calculated with HF theory and experimental data. For the reactions considered herein, it is found that the WE theory and HF method are in reasonable agreement below the two neutron separation energy assuming an energy dependent branching ratio for intermediate and heavy nuclei. In addition, qualitative confidence of WE theory for electromagnetic dissociation (EMD) cross section calculations was found. - Author-Highlights: • The Weisskopf–Ewing (WE) theory is reviewed. • Photonuclear cross sections calculated with WE theory are compared to HF predictions. • The WE theory and the HF method give similar photonuclear cross sections. • Qualitative confidence of WE theory for EMD cross section calculations is found
Adamczyk, Anne M.; Norbury, John W.; Townsend, Lawrence W.
2013-09-01
The Weisskopf-Ewing (WE) and Hauser-Feshbach (HF) theory are statistical methods, which are often used to calculate photonuclear cross sections for compound nucleus reactions. In our past work, WE methodology was presented and photonuclear reaction cross sections for nucleon emission were calculated using WE theory. Here, our previous results, which neglect pre-equilibrium emissions and do not include multiple particle emission, are compared to those calculated with HF theory and experimental data. For the reactions considered herein, it is found that the WE theory and HF method are in reasonable agreement below the two neutron separation energy assuming an energy dependent branching ratio for intermediate and heavy nuclei. In addition, qualitative confidence of WE theory for electromagnetic dissociation (EMD) cross section calculations was found. The Weisskopf-Ewing (WE) theory is reviewed. Photonuclear cross sections calculated with WE theory are compared to HF predictions. The WE theory and the HF method give similar photonuclear cross sections. Qualitative confidence of WE theory for EMD cross section calculations is found.
Heavy Ion SEU Cross Section Calculation Based on Proton Experimental Data, and Vice Versa
Wrobel, F; Pouget, V; Dilillo, L; Ecoffet, R; Lorfèvre, E; Bezerra, F; Brugger, M; Saigné, F
2014-01-01
The aim of this work is to provide a method to calculate single event upset (SEU) cross sections by using experimental data. Valuable tools such as PROFIT and SIMPA already focus on the calculation of the proton cross section by using heavy ions cross-section experiments. However, there is no available tool that calculates heavy ion cross sections based on measured proton cross sections with no knowledge of the technology. We based our approach on the diffusion-collection model with the aim of analyzing the characteristics of transient currents that trigger SEUs. We show that experimental cross sections could be used to characterize the pulses that trigger an SEU. Experimental results allow yet defining an empirical rule to identify the transient current that are responsible for an SEU. Then, the SEU cross section can be calculated for any kind of particle and any energy with no need to know the Spice model of the cell. We applied our method to some technologies (250 nm, 90 nm and 65 nm bulk SRAMs) and we sho...
Piñera, Ibrahin, E-mail: ipinera@ceaden.edu.cu [Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear, CEADEN, 30 St. 502, Playa 11300, Havana (Cuba); Cruz, Carlos M.; Leyva, Antonio; Abreu, Yamiel; Cabal, Ana E. [Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear, CEADEN, 30 St. 502, Playa 11300, Havana (Cuba); Espen, Piet Van; Remortel, Nick Van [University of Antwerp, CGB, Groenenborgerlaan 171, 2020 Antwerpen (Belgium)
2014-11-15
Highlights: • We present a calculation procedure for dpa cross section in solids under irradiation. • Improvement about 10–90% for the gamma irradiation induced dpa cross section. • Improvement about 5–50% for the electron irradiation induced dpa cross section. • More precise results (20–70%) for thin samples irradiated with electrons. - Abstract: Several authors had estimated the displacements per atom cross sections under different approximations and models, including most of the main gamma- and electron-material interaction processes. These previous works used numerical approximation formulas which are applicable for limited energy ranges. We proposed the Monte Carlo assisted Classical Method (MCCM), which relates the established theories about atom displacements to the electron and positron secondary fluence distributions calculated from the Monte Carlo simulation. In this study the MCCM procedure is adapted in order to estimate the displacements per atom cross sections for gamma and electron irradiation. The results obtained through this procedure are compared with previous theoretical calculations. An improvement in about 10–90% for the gamma irradiation induced dpa cross section is observed in our results on regard to the previous evaluations for the studied incident energies. On the other hand, the dpa cross section values produced by irradiation with electrons are improved by our calculations in about 5–50% when compared with the theoretical approximations. When thin samples are irradiated with electrons, more precise results are obtained through the MCCM (in about 20–70%) with respect to the previous studies.
Highlights: • We present a calculation procedure for dpa cross section in solids under irradiation. • Improvement about 10–90% for the gamma irradiation induced dpa cross section. • Improvement about 5–50% for the electron irradiation induced dpa cross section. • More precise results (20–70%) for thin samples irradiated with electrons. - Abstract: Several authors had estimated the displacements per atom cross sections under different approximations and models, including most of the main gamma- and electron-material interaction processes. These previous works used numerical approximation formulas which are applicable for limited energy ranges. We proposed the Monte Carlo assisted Classical Method (MCCM), which relates the established theories about atom displacements to the electron and positron secondary fluence distributions calculated from the Monte Carlo simulation. In this study the MCCM procedure is adapted in order to estimate the displacements per atom cross sections for gamma and electron irradiation. The results obtained through this procedure are compared with previous theoretical calculations. An improvement in about 10–90% for the gamma irradiation induced dpa cross section is observed in our results on regard to the previous evaluations for the studied incident energies. On the other hand, the dpa cross section values produced by irradiation with electrons are improved by our calculations in about 5–50% when compared with the theoretical approximations. When thin samples are irradiated with electrons, more precise results are obtained through the MCCM (in about 20–70%) with respect to the previous studies
Method of calculating cross section functionals in the range of unresolved resonances
A calculational scheme is proposed to evaluate expected values of complicated cross section functionals in the range of unresolved resonances. The scheme is based on the introduction of intermediate values - cross section momenta, which are calculated using optimization of parameters of the low-order gaussian quadrature formulae. Orientation of the parameters with respect to specific functionals allows to lessen significantly the number of integration modes, and, therefore, the calculational time. In addition, the scheme allows to evaluate the error bars of the calculations
Pritychenko, B.; Mughabghab, S.F.
2012-01-01
We present calculations of neutron thermal cross sections, Westcott factors, resonance integrals, Maxwellian-averaged cross sections and astrophysical reaction rates for 843 ENDF materials using data from the major evaluated nuclear libraries and European activation file. Extensive analysis of newly-evaluated neutron reaction cross sections, neutron covariances, and improvements in data processing techniques motivated us to calculate nuclear industry and neutron physics quantities, produce s-...
Calculated cross sections for transport coefficients of H 2 dilute in He and HI gas
Schaefer, J.
2010-08-01
Relaxation cross sections determining transport coefficients of the binary systems He-H 2 and HI-H 2 have been calculated by using the Waldmann-Snider formalism of the linearized collision operator. After starting with the rotational relaxation times, which are determined by inelastic rotational transitions only, all the following contributions of relaxation cross sections to the binary transport coefficients of the viscosity, heat conductivity, and diffusion have been confined to the valid isotropic approximations, i.e. containing results of elastic collisions, which are only slightly corrected by inelastic effects. Cross sections of the pure gas components have not been done in this paper. The prepared input data have been differential cross sections of a sufficient number of energies and enough initial rotational j states of the molecules to produce converged results at temperatures from 5 K up to 1000 K. Convergence with regard to the contributed j states are shown in figures, the resulting numbers of the cross sections are printed in tables for temperatures up to 600 K. The results show almost identical cross sections for the ortho-H 2 and para-H 2 gas components in relaxation cross sections of purely translational motion, whereas cross sections pertaining purely internal rotational motion are significantly different for para-H 2 and ortho-H 2, and cross sections pertaining coupling of rotational-translational motion could be shown to be negligible as demonstrated in figures.
Parameter-free calculation of charge-changing cross sections at high energy
Suzuki, Y.; Horiuchi, W.; Terashima, S.; Kanungo, R.; Ameil, F.; Atkinson, J.; Ayyad, Y.; Cortina-Gil, D.; Dillmann, I.; Estradé, A.; Evdokimov, A.; Farinon, F.; Geissel, H.; Guastalla, G.; Janik, R.; Knoebel, R.; Kurcewicz, J.; Litvinov, Yu. A.; Marta, M.; Mostazo, M.; Mukha, I.; Nociforo, C.; Ong, H. J.; Pietri, S.; Prochazka, A.; Scheidenberger, C.; Sitar, B.; Strmen, P.; Takechi, M.; Tanaka, J.; Tanihata, I.; Vargas, J.; Weick, H.; Winfield, J. S.
2016-07-01
Charge-changing cross sections at high energies are expected to provide useful information on nuclear charge radii. No reliable theory to calculate the cross section has yet been available. We develop a formula using Glauber and eikonal approximations and test its validity with recent new data on carbon isotopes measured at around 900 A MeV. We first confirm that our theory reproduces the cross sections of 12,13,14C+12C consistently with the known charge radii. Next we show that the cross sections of C-1912 on a proton target are all well reproduced provided the role of neutrons is accounted for. We also discuss the energy dependence of the charge-changing cross sections.
Calculated cross sections for transport coefficients of H2 dilute in He and HI gas
Graphical abstract: Transport coefficients of mixed gases like isotropic diffusion of hydrogen in helium gas are determined by relaxation cross sections model calculations in astrophysics: the three gas components H2, HI, and He of the Waldmann-Snider theory. - Abstract: Relaxation cross sections determining transport coefficients of the binary systems He-H2 and HI-H2 have been calculated by using the Waldmann-Snider formalism of the linearized collision operator. After starting with the rotational relaxation times, which are determined by inelastic rotational transitions only, all the following contributions of relaxation cross sections to the binary transport coefficients of the viscosity, heat conductivity, and diffusion have been confined to the valid isotropic approximations, i.e. containing results of elastic collisions, which are only slightly corrected by inelastic effects. Cross sections of the pure gas components have not been done in this paper. The prepared input data have been differential cross sections of a sufficient number of energies and enough initial rotational j states of the molecules to produce converged results at temperatures from 5 K up to 1000 K. Convergence with regard to the contributed j states are shown in figures, the resulting numbers of the cross sections are printed in tables for temperatures up to 600 K. The results show almost identical cross sections for the ortho-H2 and para-H2 gas components in relaxation cross sections of purely translational motion, whereas cross sections pertaining purely internal rotational motion are significantly different for para-H2 and ortho-H2, and cross sections pertaining coupling of rotational-translational motion could be shown to be negligible as demonstrated in figures.
In the frame of IFMIF/EVEDA activities, a prototype accelerator delivering a high power deuteron beam is under construction in Japan. Interaction of these deuterons with matter will generate high levels of neutrons and induced activation, whose predicted yields depend strongly on the models used to calculate the different cross sections. A benchmark test was performed to validate these data for deuteron energies up to 20 MeV and to define a reasonable methodology for calculating the cross sections needed for EVEDA. Calculations were performed using the nuclear models included in MCNPX and PHITS, and the dedicated nuclear model code TALYS. Although the results obtained using TALYS (global parameters) or Monte Carlo codes disagree with experimental values, a solution is proposed to compute cross sections that are a good fit to experimental data. A consistent computational procedure is also suggested to improve both transport simulations/prompt dose and activation/residual dose calculations required for EVEDA.
Dirac R-matrix calculations of photoionization cross-sections of Ni XIII
Sardar, S.; Bilal, M.; Bari, M. A.; Nazir, R. T.; Hannan, A.; Salahuddin, M.; Nasim, M. H.
2016-05-01
In this paper, we report total photoionization cross-sections of Ni XIII in the ground state (3P2) and four excited states (3P1,0, 1D2, 1S0) for the first time over the photon energy range 380-480 eV. The target wavefunctions are constructed with fully relativistic atomic structure GRASP code. Our calculated energy levels and oscillator strengths of core ion Ni XIV agree well with available experimental and theoretical results. The ionization threshold value of ground state of Ni XIII is found to be more closer to the experimental ionization energy and improved over the previous calculations. The photoionization cross-sections are calculated using the fully relativistic DARC code with an appropriate energy step of 0.01 eV to delineate the resonance structures. The calculated ionization cross-sections are important for the modelling of features of photoionized plasmas and for stellar opacities.
Blideanu, Valentin [Commissariat a l' energie atomique CEA/IRFU, Centre de Saclay, 91191 Gif sur Yvette cedex (France); Garcia, Mauricio [Universidad Nacional de Educacion a Distancia, UNED, Madrid (Spain); Instituto de Fusion Nuclear, UPM, Madrid (Spain); Joyer, Philippe, E-mail: philippe.joyer@cea.fr [Commissariat a l' energie atomique CEA/IRFU, Centre de Saclay, 91191 Gif sur Yvette cedex (France); Lopez, Daniel; Mayoral, Alicia; Ogando, Francisco [Universidad Nacional de Educacion a Distancia, UNED, Madrid (Spain); Instituto de Fusion Nuclear, UPM, Madrid (Spain); Ortiz, Felix [Universidad Nacional de Educacion a Distancia, UNED, Madrid (Spain); Sanz, Javier; Sauvan, Patrick [Universidad Nacional de Educacion a Distancia, UNED, Madrid (Spain); Instituto de Fusion Nuclear, UPM, Madrid (Spain)
2011-10-01
In the frame of IFMIF/EVEDA activities, a prototype accelerator delivering a high power deuteron beam is under construction in Japan. Interaction of these deuterons with matter will generate high levels of neutrons and induced activation, whose predicted yields depend strongly on the models used to calculate the different cross sections. A benchmark test was performed to validate these data for deuteron energies up to 20 MeV and to define a reasonable methodology for calculating the cross sections needed for EVEDA. Calculations were performed using the nuclear models included in MCNPX and PHITS, and the dedicated nuclear model code TALYS. Although the results obtained using TALYS (global parameters) or Monte Carlo codes disagree with experimental values, a solution is proposed to compute cross sections that are a good fit to experimental data. A consistent computational procedure is also suggested to improve both transport simulations/prompt dose and activation/residual dose calculations required for EVEDA.
Quantum calculations for photodetachment cross sections of H− in an inhomogeneous electric field
We calculate the photodetachment cross sections of H− in a gradient electric field based on traditional quantum approach. The system provides a rare example that the formulas for the cross sections can be explicitly derived by both the quantum approach and closed-orbit theory. The quantum results are compared with those of the closed-orbit theory. The correct phase values in the closed-orbit theory are essential and necessary to produce accurate cross sections. Our quantum results remove some previous ambiguities in assigning the phase values in the closed-orbit theory (G. C. Yang and M. L. Du 2007 Phys. Rev. A 75 029904E). (atomic and molecular physics)
Results of coupled channels calculations for the neutrons cross sections of a set of actinide nuclei
This report gathers recents results of neutrons interactions with the following actinide nuclei: 230Th, 232Th, 234U, 238U, 242Pu, 246Cm and 252Cf from the use of the coupled channels optical model. Tabulations of the following quantities are given in Annexe: total, direct elastic and inelastic scattering (integrated and differential), and compound nucleus formation cross sections; ground state generalized transmission coefficients needed to calculate the cross sections of partial compound nucleus processes. This work was carried out within the framework of the IAEA-NDS Coordinated Research Programme on the Intercomparison of Actinide Neutron Cross Section Evaluations
CREST : a computer program for the calculation of composition dependent self-shielded cross-sections
A computer program CREST for the calculation of the composition and temperature dependent self-shielded cross-sections using the shielding factor approach has been described. The code includes the editing and formation of the data library, calculation of the effective shielding factors and cross-sections, a fundamental mode calculation to generate the neutron spectrum for the system which is further used to calculate the effective elastic removal cross-sections. Studies to explore the sensitivity of reactor parameters to changes in group cross-sections can also be carried out by using the facility available in the code to temporarily change the desired constants. The final self-shielded and transport corrected group cross-sections can be dumped on cards or magnetic tape in a suitable form for their direct use in a transport or diffusion theory code for detailed reactor calculations. The program is written in FORTRAN and can be accommodated in a computer with 32 K work memory. The input preparation details, sample problem and the listing of the program are given. (author)
Program POD. A computer code to calculate cross sections for neutron-induced nuclear reactions
A computer code, POD, was developed for neutron-induced nuclear data evaluations. This program is based on four theoretical models, (1) the optical model to calculate shape-elastic scattering and reaction cross sections, (2) the distorted wave Born approximation to calculate neutron inelastic scattering cross sections, (3) the preequilibrium model, and (4) the multi-step statistical model. With this program, cross sections can be calculated for reactions (n, γ), (n, n'), (n, p), (n, α), (n, d), (n, t), (n, 3He), (n, 2n), (n, np), (n, nα), (n, nd), and (n, 3n) in the neutron energy range above the resonance region to 20 MeV. The computational methods and input parameters are explained in this report, with sample inputs and outputs. (author)
Basis calculation of phase cross section library in a low power fast reactor neutronic simulation
In order to implement the utilization of the efficient multidimensional cubic SPLINE interpolation, we determine the phase library bases for net like relevant state components. A generic cubic surface and a weighted plane pertinent alternative interpolating methods used capable to generate cross sections values for fixed coordinates from cell code calculated data points is used. It is verified that the phase library bases increases or decrease smoothly and monotonically with the spectrum asymmetry and total flux buckling. This justifies its use in cross section updating avoiding cell calculations. (author)
Measurement and calculation of the 233Pa fission cross-section for advanced fuel cycles
The energy dependence of the neutron-induced fission cross-section of 233Pa has been measured directly for the first time from the fission threshold up to 8.5 MeV. This fission cross-section is a key ingredient in feasibility studies on fast reactors and accelerator driven systems based on the Th-U fuel cycle. The results are at strong variance with the existing evaluations. The new experimental data give lower cross-section values and resolve the question about the threshold energy. Additionally a new theoretical calculation of the reaction cross-section has been performed with the statistical model code STATIS, showing a very good agreement with the experimental data. (authors)
Recently, the development of photoelectron velocity map imaging makes it much easier to obtain the photoelectron angular distributions (PADs) experimentally. However, explanations of PADs are only qualitative in most cases, and very limited works have been reported on how to calculate PAD of anions. In the present work, we report a method using the density-functional-theory Kohn-Sham orbitals to calculate the photodetachment cross sections and the anisotropy parameter β. The spherical average over all random molecular orientation is calculated analytically. A program which can handle both the Gaussian type orbital and the Slater type orbital has been coded. The testing calculations on Li−, C−, O−, F−, CH−, OH−, NH2−, O2−, and S2− show that our method is an efficient way to calculate the photodetachment cross section and anisotropy parameter β for anions, thus promising for large systems
Talys calculations for evaluation of neutron-induced single-event upset cross sections
The computer code TALYS has been used to calculate interactions between cosmic-ray neutrons and silicon nuclei with the goal to describe single-event upset (SEU) cross sections in microelectronics devices. Calculations for the Si(n,X) reaction extend over an energy range of 2 to 200 MeV. The obtained energy spectra of the resulting residuals and light-ions have been integrated using several different critical charges as SEU threshold. It is found that the SEU cross section seems largely to be dominated by 28Si recoils from elastic scattering. Furthermore, the shape of the SEU cross section as a function of the energy of the incoming neutron changes drastically with decreasing critical charge. The results presented in this report stress the importance of performing studies at mono-energetic neutron beams to advance the understanding of the underlying mechanisms causing SEUs
Calculation of Total Cross Sections for Positron Scattering by Lithium at Intermediate Energies
WU Yong; ZHOU Ya-Jun
2005-01-01
@@ The total cross sections for positron scattering by lithium at intermediate energies (10-200eV) are calculated by using the coupled-channel optical method with a complex equivalent-local polarization potential which incorporates ionization continuum and positronium (Ps) formation channels contributions into the coupled channels framework.The effects of the two-body Ps rearrangement and three-body ionization process on the total cross section are found to be significant at lower energies and this effect is not negligible up to 30eV.Compared to the available theoretical data, the predicted total cross sections agree quite well with the calculations of McAlinden et al.
Higher order perturbative QCD calculation of jet cross sections in e+e- annihilation
We present in detail the analytic calculation of the Sterman-Weinberg type 3-jet cross section to order αsub(s)2. The fit to recent PLUTO data gives in the MS scheme αsub(s) = 0.17 which corresponds to Λ = 0.24 GeV in the 1-loop approximation. (orig.)
Compton cross-section calculations in terms of recoil-ion momentum observables
Kaliman, Z. E-mail: kaliman@pefri.hr; Pisk, K
2004-11-01
We present a theoretical framework for the calculations of Compton scattering on bound electrons, based on recoil-ion observables. We show the results for Compton cross sections on He-atom, with respect to the recoil-ion momentum. The validity and the utility of this approach are discussed particularly in connection with the electron momentum density determination.
First step in the process of calculating the cross section for muonic antihydrogen
Maher, Niamh
2016-01-01
The end goal of the project is to measure the charge radius of the antiproton with muons. However a necessary step first is to calculate cross section of Muonium and antiprotons in the production of antihydrogen to determine the feasibility of such an experiment.
Calculation of differential cross section for dielectronic recombination with two-electron uranium
Lyashchenko, Konstantin N.; Andreev, Oleg Yu.
2016-01-01
Calculation of the differential cross section for the dielectronic recombination with two-electron uranium within the framework of QED is presented. The polarization of the emitted photon is investigated. The contributions of the Breit interaction and the interference of the photon multipoles are studied.
A modified plane wave model for calculating UV photo-ionization cross-sections
Beerlage, M.J.M.; Feil, D.
1977-01-01
Photoionization cross-sections are calculated for a number of molecules, using a plane wave method. Agreement with experimental data is considerably improved with respect to common plane wave results if the energy of the photoelectron is assumed to equal the incident photon energy.
Cross section calculations of astrophysical interest. [for theories of absorption and emission lines
Gerjuoy, E.
1974-01-01
Cross sections are discussed for rotational excitation associated with theories of absorption and emission lines from molecules in space with emphasis on H2CO, CO, and OH by collisions with neutral particles such H, H2, and He. The sensitivity of the Thaddeus equation for the H2CO calculation is examined.
New techniques for multi-level cross section calculation and fitting
A number of recent developments in multi-level cross section work are described. A new iteration scheme for the conversion of Reich-Moore resonance parameters to Kapur-Peierls parameters allows application of Turing's method for Gaussian broadening of meromorphic functions directly to multi-level cross section expressions, without recourse to the Voigt profiles psi and chi. This makes calculation of Doppler-broadened Reich-Moore and MLBW cross sections practically as fast as SLBW and Adler-Adler cross section calculations involving the Voigt profiles. A convenient distant-level treatment utilizing average resonance parameters is presented. Apart from effectively dealing with edge effects in resonance fitting work it also leads to a simple prescription for the determination of bound levels which reproduce the thermal cross sections correctly. A brief discussion of improved resonance shape fitting techniques is included, with empahsis on the importance of correlated errors and proper use of prior information by application of Bayes' theorem. (orig.)
Qualification of KENO calculations with ENDF/B-V cross sections
The Commercial Nuclear Fuel Division of Westinghouse used KENO calculations as the basis for criticality safety analysis to cover the transportation and storage of nuclear fuel. The calculational code sequence was requalified in 1986. The basic cross-section set was changed from the ENDF/B-IV data set to the CSRL-V data. This paper discusses the benchmark effort, the results, and the application of the results to criticality analyses
AMD Calculation of the double differential cross section for nucleon-12C reaction
So far at the time of exposure assessment, heavy ions have not been regarded as important, but due to the realization of manned space flight and the cancer treatment using heavy ions, their importance has increased. However, by existing transport calculation code, the information required for evaluating heavy ion exposure, namely double differential cross section for every fragment, is difficult to be obtained. Therefore, by paying attention to antisymmetrized version of molecular dynamics (AMD) which is the simulation method for heavy ion reaction, it was set as the purpose of this research to evaluate its accuracy. In this research, the collision of nucleons with 12C was simulated by AMD method, and the calculation of double differential cross section was carried out. In order to reduce the time for calculation, the incidence of nucleons and the carbon that is one of the compositions of human bodies were selected. The framework of the AMD method, the procedure of calculation by the AMD method and the results of calculation are reported. The calculated value of the double differential cross section of 12C(p,nX) reaction agreed with good accuracy with the experimental value. (K.I.)
The molecular stopping cross sections of hydrogen sulfide, methyl sulfide, methyl disulfide, carbon disulfide, ethylene sulfide, proplene sulfide, trimethylene sulfide, thiophene, and sulfur hexafluoride have beem measured for 0.3--2.0 MeV He+ ions. It is shown that the bond order correlation for the third period element sulfur is qualitatively in agreement with its second row counterpart, oxygen, but that the stopping cross-section dependence on bond order is considerably less (approx. =5% in sulfur compared to approx. =17% in oxygen). In the energy region where the stopping contribution of the valence electrons is largest, the atomic stopping cross sections of sulfur for double-bonded, ring-structured, and single-bonded compounds decrease in the order epsilon/sub DB/(S)>epsilon/sub RING/(S)>epsilon/sub SB/(S), a trend consistent with that observed for oxygen and carbon. The experimental results suggest a minimum d-orbital involvement in SF6 and reveal a lower peak energy E/sub peak/ and width delta when S exists in the compound than when C, O, or F are present
HATHOR. HAdronic Top and Heavy quarks crOss section calculatoR
We present a program to calculate the total cross section for top-quark pair production in hadronic collisions. The program takes into account recent theoretical developments such as approximate next-to-next-to-leading order perturbative QCD corrections and it allows for studies of the theoretical uncertainty by separate variations of the factorization and renormalization scales. In addition it offers the possibility to obtain the cross section as a function of the running top-quark mass. The program can also be applied to a hypothetical fourth quark family provided the QCD couplings are standard. (orig.)
Rovibrational cross sections from reactance matrices calculated in adiabatic nuclei approximation
Body frame reactance matrices obtained from elastic scattering calculations at fixed internuclear separations are transformed into laboratory frame matrices to compute differential and integral cross sections for simultaneous rotational and vibrational excitation of a molecule. Transformation for vibrational excitation is obtained by integrating the real and imaginary parts of the body-frame t-matrices over internuclear separation. Vibrational wave functions are assumed to be given. The rotational transformation involves an eight-fold sum over angular momenta. The summands involve Asub(lambda)-coefficients and Legendre polynomials, which are each evaluated by separate subprograms. Differential, integral, and momentum transfer cross sections are computed from the transformed t-matrices. (Auth.)
A program package for computer calculations of spallation, fission and fragmentation reactions cross sections by means of activation analysis has been created. Several complements to the method have been made, the role of single and double escape peaks contributions to γ-lines of the residual nuclei and also dependence of the cross sections on the spectrometer deadtime have been taken into account. A way for complete identification of all the γ-lines of nuclei produced has been proposed based on an internal intensity ratio using a nuclear data base. (author)
Cross section calculation for electron impact ionization and elastic scattering from cisplatin
One of the drugs which is typically used in chemotherapy is cisplatin (H6N2Cl2Pt). Chemotherapy is often successfully connected with the ionizing radiation treatment. Our work deals with the elastic electron scattering and electron impact ionization of cisplatin molecule. Total cross section for single electron-impact ionization of cisplatin molecule has been calculated with the binary-encounter-Bethe (BEB) model from the ionization threshold up to 5 keV. To obtain input data for the BEB calculations, geometric and electronic structures of the cisplatin have been studied with quantum chemical methods. Elastic cross section for electron collisions with cisplatin have also been evaluated using independent atom method with static-polarization model potential for incident energies ranging from 50 to 3000 eV. The obtained geometric structure of cisplatin is compared with available experimental and theoretical data. Calculated cross sections have been compared with related cross sections for selected purine and pyrimidine bases, they appear to be similar in values
Dirac R-matrix calculations of photoionization cross-sections of Ca IV
Nazir, R. T.; Bari, M. A.; Sardar, S.; Bilal, M.; Salahuddin, M.; Nasim, M. H.
2016-08-01
In this paper total photoionization cross sections in the ground (^2P^o_{3/2}) and two meta-stable states (^2P^o_{1/2},^2S_{1/2}) of Ca IV are reported using the relativistic Dirac Atomic R-matrix Codes (DARC) in the photon energy range 67-122 eV. The target wavefunctions are constructed with fully relativistic atomic structure GRASP package. A total of lowest lying 48 fine-structure levels arising from the four main configuration (3s23p4, 3s3p5 3s23p33d, 3p6) are considered for the target wavefunctions expansion. Our calculated eigenvalues of the core ion Ca V show reasonable agreement with available experimental and theoretical results. It is found that present ionization threshold energies of first three levels of Ca IV are in excellent agreement with NIST energies and experimental measurements. The photoionization cross sections of Ca IV are calculated with an appropriate energy step (0.1× 10-3 eV) to describe the resonance structures in vivid details. A comparison for the statistically weighted mixture of states (^2P^o_{3/2},^2P^o_{1/2}) with other experimental measurements including term-resolved ground state theoretical calculations is presented. Our computed photoionization cross sections agree better with the measured cross sections than the other theoretical approaches and are potentially more accurate.
MC2-2: a code to calculate fast neutron spectra and multigroup cross sections
MC2-2 is a program to solve the neutron slowing down problem using basic neutron data derived from the ENDF/B data files. The spectrum calculated by MC2-2 is used to collapse the basic data to multigroup cross sections for use in standard reactor neutronics codes. Four different slowing down formulations are used by MC2-2: multigroup, continuous slowing down using the Goertzel-Greuling or Improved Goertzel-Greuling moderating parameters, and a hyper-fine-group integral transport calculation. Resolved and unresolved resonance cross sections are calculated accounting for self-shielding, broadening and overlap effects. This document provides a description of the MC2-2 program. The physics and mathematics of the neutron slowing down problem are derived and detailed information is provided to aid the MC2-2 user in preparing input for the program and implementation of the program on IBM 370 or CDC 7600 computers
A nuclear cross section calculation system with simplified input-format, version I
To calculate the nuclear cross sections with a statistical and preequilibrium model as efficiently and easily as possible, a calculation system with simplified input-format has been developed. The system is composed of the ELIESE-GNASH joint program and the DWUCK program. A set of global optical model potential parameters is programmed in the codes. The discrete level data are prepared from ENSDF file after correction and input-format conversion. Using the present version, neutron cross sections for 25 nuclides covering the range from 27Al to 109Ag were calculated up to 20 MeV. As the result of general agreements with experimental data for wide mass range, the availability of the present version is proved. (author)
Calculation of neutron cross sections on isotopes of yttrium and zirconium
Multistep Hauser-Feshbach calculations with preequilibrium corrections were made for neutron-induced reactions on yttrium and zirconium isotopes between 0.001 and 20 MeV. Recently new neutron cross-section data have been measured for unstable isotopes of these elements. These data, along with results from charged-particle simulation of neutron reactions, provide unique opportunities under which to test nuclear-model techniques and parameters in this mass region. A complete and consistent analysis of varied neutron reaction types using input parameters determined independently from additional neutron and charged-particle data. The overall agreement between calculations and a wide variety of experimental results available for these nuclei leads to increased confidence in calculated cross sections made where data are incomplete or lacking. 75 references
Hartree-Fock calculation of the differential photoionization cross sections of small Li clusters
Cross sections and angular distribution parameters for the single-photon ionization of all electron orbitals of Li2−8 are systematically computed in a broad interval of the photoelectron kinetic energies for the energetically most stable geometry of each cluster. Calculations of the partial photoelectron continuum waves in clusters are carried out by the single center method within the Hartree-Fock approximation. We study photoionization cross sections per one electron and analyze in some details general trends in the photoionization of inner and outer shells with respect to the size and geometry of a cluster. The present differential cross sections computed for Li2 are in a good agreement with the available theoretical data, whereas those computed for Li3−8 clusters can be considered as theoretical predictions
A new calculation formula of the nuclear cross-section of therapeutic protons
Ulmer, W
2014-01-01
We have previously developed for nuclear cross-sections of therapeutic protons a calculation model, which is founded on the collective model as well as a quantum mechanical many particle problem to derive the S matrix and transition probabilities. In this communication, we show that the resonances can be derived by shifted Gaussian functions, whereas the unspecific nuclear interaction compounds can be represented by an error function, which also provides the asymptotic behavior. The energy shifts can be interpreted in terms of necessary domains of energy to excite typical nuclear processes. Thus the necessary formulas referring to previous calculations of nuclear cross-sections will be represented in section 2. The mass number AN determines the strong interaction range. The threshold energy ETh of the energy barrier is determined by the condition Estrong = ECoulomb. A linear combination of Gaussians, which contain additional energy shifts, and an error function incorporate a possible representation of Fermi-D...
Optimization of multidimensional cross-section tables for few-group core calculations
Highlights: • Optimization of tabulated cross-sections libraries for multi-group diffusion codes. • Sensitivity coefficients using perturbation theory are determined. • A non-uniform grid satisfying a given target accuracy in k-effective is built. • Satisfactory results are obtained using libraries with different accuracy level. - Abstract: Multigroup diffusion codes for three dimensional LWR core analysis use as input data pre-generated homogenized few group cross sections and discontinuity factors for certain combinations of state variables, such as temperatures or densities. The simplest way of compiling those data are tabulated libraries, where a grid covering the domain of state variables is defined and the homogenized cross sections are computed at the grid points. Then, during the core calculation, an interpolation algorithm is used to compute the cross sections from the table values. Since interpolation errors depend on the distance between the grid points, a determined refinement of the mesh is required to reach a target accuracy, which could lead to large data storage volume and a large number of lattice transport calculations. In this paper, a simple and effective procedure to optimize the distribution of grid points for tabulated libraries is presented. Optimality is considered in the sense of building a non-uniform point distribution with the minimum number of grid points for each state variable satisfying a given target accuracy in k-effective. The procedure consists of determining the sensitivity coefficients of k-effective to cross sections using perturbation theory; and estimating the interpolation errors committed with different mesh steps for each state variable. These results allow evaluating the influence of interpolation errors of each cross section on k-effective for any combination of state variables, and estimating the optimal distance between grid points
Consistent activation cross section calculations for all stable isotopes of V, Cr, Mn, Fe, Co, Ni
Comparison of the available experimental fast neutron reaction excitation functions on all stable isotopes of the elements V, Cr, Mn, Fe, Co, and Ni with nuclear model calculations is presented. Neutron and charged-particle emission spectra have also been analyzed in order to validate the pre-equilibrium emission model calculations (with no free internal parameters). The trial procedure involved provides confidence in the nuclear-model parameter basis used and makes possible calculations of increased accuracy for activation cross sections in this mass range, required for applications. (author). 13 refs, 27 figs
Ab initio calculation of H+He+ charge-transfer cross sections for plasma physics
The charge-transfer in low-energy (0.25 to 150 eV/amu) H(nl)+He+(1s) collisions is investigated using a quasimolecular approach for the n=2,3 as well as the first two n=4 singlet states. The diabatic potential energy curves of the HeH+ molecular ion are obtained from the adiabatic potential energy curves and the nonadiabatic radial coupling matrix elements using a two-by-two diabatization method, and a time-dependent wave-packet approach is used to calculate the state-to-state cross sections. We find a strong dependence of the charge-transfer cross section on the principal and orbital quantum numbers n and l of the initial or final state. We estimate the effect of the nonadiabatic rotational couplings, which is found to be important even at energies below 1 eV/amu. However, the effect is small on the total cross sections at energies below 10 eV/amu. We observe that to calculate charge-transfer cross sections in an n manifold, it is only necessary to include states with n'≤n, and we discuss the limitations of our approach as the number of states increases.
Ab-initio calculation of the photonuclear cross section of $^{10}$B
Kruse, M K G; Johnson, C W
2015-01-01
We present for the first-time the photonuclear cross section of $^{10}$B calculated within the ab-initio No Core Shell Model framework. Realistic two-nucleon (NN) chiral forces up to next-to-next-to-next-order (N3LO), which have been softened by the similarity renormalization group method (SRG) to $\\lambda=2.02$ fm$^{-1}$, were utilized. The electric-dipole response function is calculated using the Lanczos method. The effects of the continuum were accounted for by including neutron escape widths derived from R-matrix theory. The calculated cross section agrees well with experimental data in terms of structure as well as in absolute peak height, $\\sigma_{\\rm max}=4.85~{\\rm mb}$ at photon energy $\\omega=23.61~{\\rm MeV}$, and integrated cross section $85.36\\, {\\rm MeV \\cdotp mb}$. We test the Brink hypothesis by calculating the electric-dipole response for the first five positive-parity states in $^{10}$B and verify that dipole excitations built upon the ground- and excited states have similar characteristics.
Close-coupling R-matrix calculations for electron-ion recombination cross sections
Close-coupling (CC) calculations of electron-ion recombination cross sections using the R-matrix method are presented and benchmarked with available experimental measurements. The electron-ion recombination process, including resonant and non-resonant recombination may be unified as a natural extension of the coupled-channel approximation, as traditionally employed for photoionization and electron-ion scattering. Recombination cross sections can be calculated to the same accuracy by employing similar eigenfunction expansions for the target ion. Detailed results are obtained for electron recombination with C V, C VI, O VIII and Fe XXV. Several sets of theoretical calculations are reported and discussed: non-relativistic CC in LS coupling, relativistic CC in the Breit-Pauli approximation, with radiative attenuation and fine structure, and the relativistic distorted-wave approximation. The theoretical results are in very good agreement with highly accurate experimental measurements at the Heidelberg test storage ring for C V, C VI and O VIII, and the electron-ion beam trap at Livermore for Fe XXV. We discuss the overall effect of radiation damping of all resonances on effective cross sections and rates, important for H- and He-like ions. In addition to agreement with experimental data, the validity of the CC calculations is demonstrated by the continuity between the calculated photorecombination, dielectronic recombination and electron impact excitation cross sections. Certain issues related to the works of Badnell et al (1998 J. Phys. B: At. Mol. Opt. Phys. 31 L239) and Robicheaux (1998 J. Phys. B: At. Mol. Opt. Phys. 31 L109) are also addressed. (author)
Faddeev calculations of pμ+p collisions: Effect of hyperfine splitting on the cross sections
The Faddeev equations, modified to remove long-range coupling between different channels, are solved in the total-angular-momentum representation for pμ + p collisions. S-wave elastic and hyperfine-transition cross sections are calculated with and without explicit inclusion of the hyperfine splitting ΔE. For hyperfine quenching the simpler approach without hyperfine splitting is found adequate at collision energies above about ΔE, but for elastic scattering it becomes adequate at somewhat higher energies. The present cross sections tend to fall in between earlier calculations done using a large Standard adiabatic expansion and those done using a two-state improved adiabatic expansion, but are closer to the former
Level alignment in CIII ions: R-matrix calculations of m-resolved excitation cross section
The polarization of emission lines from plasma in addition to their intensities is the source of data for the interpretation of plasma characteristics. The population-alignment collisional-radiative (PACR) model code has been developed for the interpretation of the experimental observations in terms of the anisotropic electron velocity distribution in plasma. The PACR model is implemented to calculate m-resolved excitation cross section for the following transition in Be-like CIII ions; (i) from ground state 1s22s21S0 to 1s22s3p 3P0,1,2 and (ii) from metastable 1s22s2p 3P0,12 to 1s22s3p 3P0,1,2. The calculation is performed by two code; RMATRX and SCATTAMPREL modified to extract m-resolved excitation cross section. (Y. Kazumata)
Calculated neutron-induced cross sections for 53Cr from 1 to 20 MeV
Neutron-induced cross sections of 53Cr have been calculated in the energy regions from 1 to 20 MeV. The quantities obtained are the cross sections for the reactions (n,n'γ), (n,2n), (n,np), (n,nα), (n,pγ), (n,pn), (n,αγ), (n,αn), (n,d), (n,t), (n,3He), and (n,γ), as well as the spectra of emitted neutrons, protons, alpha particles, and gamma rays. The precompound process was included above 5 MeV in addition to the compound process. For the inelastic scattering, the contribution of the direct interaction was calculated with DWBA. 36 refs., 23 figs., 11 tabs
A Complete Order-$\\alpha^3$ Calculation of the Cross Section for Polarized Compton Scattering
Swartz, M L
1998-01-01
The construction of a computer code to calculate the cross sections for the spin-polarized processes e-gamma=>e-gamma,e-gamma-gamma,e-e+e- to order-alpha**3 is described. The code calculates cross sections for circularly-polarized initial-state photons and arbitrarily polarized initial-state electrons. The application of the code to the SLD Compton polarimeter indicates that the order-alpha**3 corrections produce a fractional shift in the SLC polarization scale of -0.1% which is too small and of the wrong sign to account for the discrepancy in the Z-pole asymmetries measured by the SLD Collaboration and the LEP Collaborations.
Photoionization cross section calculations for the halogen-like ions Kr$^+$ and Xe$^+$
McLaughlin, B M
2012-01-01
Photoionization cross sections calculations on the halogen-like ions; Kr$^+$ and Xe$^+$ have been performed for a photon energy range from each ion threshold to 15 eV, using large-scale close-coupling calculations within the Dirac-Coulomb R-matrix approximation. The results from our theoretical work are compared with recent measurements made at the ASTRID merged-beam set-up at the University of Aarhus in Denmark and from the Fourier transform ion cyclotron resonance (FT-ICR) trap method at the SOLEIL synchrotron radiation facility in Saint-Aubin, France and the Advanced Light Soure (ALS). For each of these complex ions our theoretical cross section results over the photon energy range investigated are seen to be in excellent agreement with experiment. Resonance energy positions and quantum defects of the prominent Rydberg resonances series identified in the spectra are compared with experiment for these complex halogen like-ions.
PEGASUS, a preequilibrium and evaporation theory code, was developed which calculates 17 neutron reaction cross sections, the particle spectra and the double differential cross sections. The code is suited to a rapid and scoping calculation. Theoretical model and the some results of calculation are presented. (author)
The calculations of total cross sections of electron capture in collisions of Cq+ with H(1s) are reviewed. At low collision energies, new calculations have been performed, using molecular expansions, to analyze isotope effects. The Classical Trajectory Monte Carlo method have been also applied to discuss the accuracy of previous calculations and to extend the energy range of the available cross sections
Effect of XCOM photoelectric cross-sections on dosimetric quantities calculated with EGSnrc
The EGSnrc Monte-Carlo code system incorporates improved low energy photon physics such as atomic relaxations and the implementation of bound Compton cross-sections using the impulse approximation. The total cross-section for photoelectric absorption however, still relies on the data by Storm and Israel (S and I). Yet, low energy applications such as brachytherapy (e.g. 125I) require up-to-date low-energy photoelectric cross-section data. In this paper, we study the dosimetric effects of a simple implementation of NIST XCOM-based photoelectric cross-sections in EGSnrc. This is done by calculating mass energy-absorption coefficients, absorbed dose from point sources, kilovoltage x-ray beams and ion chamber response. In the EGS code system, the PEGS4 routine reads the photoelectric and pair cross-sections for elements from a file (pgspepr.dat) and provides numerical fits for compounds which will be used by EGSnrc. We updated the photoelectric cross-sections of the pgspepr.dat file with the XCOM total photoelectric absorption cross-sections from NIST. After validation of this new implementation, we studied its effects on a number of dosimetrically relevant quantities. Firstly, we calculated mass energy-absorption coefficients by scoring energy transferred in a thin slab of water and air using the DOSRZnrc user code. Secondly, we calculated inverse-square corrected absorbed dose distributions from point sources in water by using an internally developed user code, KERNELph. Thirdly, we studied the differences in free-air ion chamber response calculations. Ion chamber response is defined as the dose to the cavity of an ionization chamber, Dgas, positioned with its effective point of measurement at a reference point divided by air-kerma measured free-in-air at the same point. The ion chamber response was calculated using monoenergetic photon beams of energy 10 keV to 200 keV. The comparison of the Storm and Israel photoelectric cross-sections with the XCOM cross-sections
Kendl, Alexander
2014-01-01
Turbulent transport of trace impurities impurities in the edge and scrape-off-layer of tokamak fusion plasmas is modelled by three dimensional electromagnetic gyrofluid computations including evolution of plasma profile gradients. The source function of impurity ions is dynamically computed from pre-determined measured and calculated electron impact ionization cross section data. The simulations describe the generation and further passive turbulent E-cross-B advection of the impurities by intermittent fluctuations and coherent filamentary structures (blobs) across the scrape-off-layer.
Calculation of triple differential cross sections in electron scattering on atomic hydrogen
Calculations of the triple differential cross sections for electrons scattering on the ground state of atomic hydrogen at incident energies of 54.4 and 150 eV is presented. The Convergent Close-Coupling (CCC) method is used. For this target the method is essentially without approximation. The total wave function was expanded in an ever increasing Laguerre basis until convergence has been obtained. A generally good agreement with experiment was found, but some quantitative discrepancies remain. 15 refs., 2 figs
Contrasts in the application of distortion in calculations of the K-shell ionization cross section
Two models which describe the proton-induced ionization from the K shell of an atom are contrasted in terms of the differing forms of distortion employed. Results of calculations of both total and differential cross section are seen to be surprisingly close despite the large disparity between the models. Some consequences are discussed, particularly with regard to the use of pseudostates to represent continuum states. (orig.)
Effects of shape differences in the level densities of three formalisms on calculated cross-sections
Effects of shape differences in the level densities of three formalisms on calculated cross-sections and particle emission spectra are described. Reactions for incident neutrons up to 20 MeV on 58Ni are chosen for illustrations. Level density parameters for one of the formalisms are determined from the available neutron resonance data for one residual nuclide in the binary channels and from fitting the measured (n,n'), (n,p) and (n,α) cross-sections for the other two residual nuclides. Level density parameters for the other two formalisms are determined such that they yield the same values as the above one at two selected energies. This procedure forces the level densities from the three formalisms used for the binary pat of the calculation to be as close as possible. The remaining differences are in their energy dependences (shapes). It is shown that these shape differences alone are enough to cause the calculated cross-sections and particle emission spectra to be different by up to 60%. (author)
Effects of shape differences in the level densities of three formalisms of calculated cross sections
Effects of shape differences in the level densities of three formalisms on calculated cross sections and particle emission spectra are described. Reactions for incident neutrons up to 20 MeV on 58Ni are chosen for illustrations. Level-density parameters for one of the formalisms are determined from the available neutron resonance data for one residual nuclide in the binary channels and from fitting the measured (n, n'), (n, p), and (n, α) cross sections for the other two residual nuclides. Level-density parameters for the other two formalisms are determined such that they yield the same values as the above one at two selected energies. This procedure forces the level densities from the three formalisms used for the binary part of the calculation to be as close as possible. The remaining differences are in their energy dependences (shapes). It is shown that these shape differences alone are enough to cause the calculated cross sections and particle emission spectra to be different by up to 60%
Smirnov Vladimir Aleksandrovich
Full Text Available The article focuses on calculating the loss factor in the stiffness corrector of quasi-zero stiffness vibration isolator, designed for precision equipment vibration isolation from low-frequency base vibrations. Stiffness corrector is a beam with a variable cross-section and an initial curvature loaded in the middle with the transverse load. The initial curvature of the beam is determined by solving the problem of the axial deformation of the beam of variable cross-section with an axial load exceeding the critical Euler force. The loss factor of the stiffness corrector’s material is determined in accordance with Panovko energy theory. For these purposes, the elastic shape of the stiffness corrector loaded with transverse force is calculated and potential energy of the corrector, which corresponds to the prescribed elastic shape, is obtained. Loss factor is calculated by dividing the absorption coefficient of the stiffness corrector material by its potential energy for various types of cross-sections of corrector’s beams. Determination of stiffness corrector’s material loss factor is performed through several experimental investigations, in which the coefficients of the approximating function are obtained via approximation of specimen of damped oscillations.
Calculation of 235U(n,n') cross sections for ENDF/B-VI
Cross sections for neutron-induced reactions on 235U between 0.01 and 20 MeV have been calculated in a preliminary analysis for the ENDF/B-VI evaluation with particular emphasis on neutron inelastic scattering. A deformed optical model potential that fits total, elastic, inelastic, and low-energy average resonance data is used to calculate direct (n,n') cross sections and transmission coefficients for a Hauser-Feshbach statistical theory analysis using a multiple fission barrier representation. Direct cross sections for higher-lying vibrational states are provided from DWBA calculations, normalized using B(E/ital l/) values determined from (d,d') and Coulomb excitation data. Initial fission barrier parameters and transition state density enhancements appropriate to the compound systems involved were obtained from previous analyses, especially fits to charged-particle fission probability data. Further modifications to fit 235U(n,f) data were small, and the final fission parameters are generally consistent with published values. The results from this preliminary analysis are compared with the ENDF/B-V evaluation as well as with experimental data. 26 refs., 5 figs., 3 tabs
Importance of level structure in nuclear reaction cross-section calculations. Revision 1
It is shown that level-density expressions cannot adequately represent or substitute for level structure information when making calculations of the Hauser-Feshbach type for cross sections or isomer-ratios for nuclei in the first few MeV above their ground state. It is stated that such discrete level information should include both experimentally confirmed and theoretically predicted levels. The utility of discrete level information to optimize level density calculations, to compute isomer ratios, in deriving dipole strength functions, and in the analysis of primary gamma ray spectra is emphasized, especially for nuclei far from the line of stability. 29 refs., 12 figs., 6 tabs
Calculation of Elastic Differential Cross Sections for Electron Scattering by Molecular Hydrogen
解廷献; 周雅君; 潘守甫; 于俊华
2001-01-01
Differential cross sections for the elastic scattering of electrons by H2 at 100 eV and 150 eV have been calculated and compared with experiments. We use the momentum space method in which the electron-molecule system has a single centre and the interaction of electron-nuclei is expanded by a multipole expansion. The static exchange calculation is supplemented by a phenomenological polarization potential. Electron-molecule scattering is reduced to an electronic problem by the Born-Oppenheimer approximation, using closure over the vibrational and rotational states.
New procedure calculation of K-shell ionization cross sections by proton impact
The database, which relies on different compilations available in the literature and on other experimental values extracted from papers published from 1992 till 2010, is used, within the individual treatment of the elements from beryllium (4Be) to uranium (92U), to deduce the empirical cross sections. These experimental data can be presented in a single curve, depending on a scaling law extracted from studies in the most familiar theories of collision (PWBA and BEA). Then, a fourth order polynomial was used to fit very well the existing database of K-shell ionization cross sections by proton. This procedure generates a new set of parameters to calculate empirical cross sections. Following the present procedure, our results are compared with those obtained using the ECPSSR model where a discrepancy is observed in the low-proton energy regime. - Highlights: → We used the experimental data to define the K-shell ionization cross sections. → These values are presented in a single curve used PWBA and BEA theories. → The empirical values are defined for each element separately.
The calculation of radial dose from heavy ions: predictions of biological action cross sections
Katz, R.; Cucinotta, F. A.; Zhang, C. X.; Wilson, J. W. (Principal Investigator)
1996-01-01
The track structure model of heavy ion cross sections was developed by Katz and co-workers in the 1960s. In this model the action cross section is evaluated by mapping the dose-response of a detector to gamma rays (modeled from biological target theory) onto the radial dose distribution from delta rays about the path of the ion. This is taken to yield the radial distribution of probability for a "hit" (an interaction leading to an observable end-point). Radial integration of the probability yields the cross section. When different response from ions of different Z having the same stopping power is observed this model may be indicated. Since the 1960s there have been several developments in the computation of the radial dose distribution, in the measurement of these distributions, and in new radiobiological data against which to test the model. The earliest model, by Butts and Katz made use of simplified delta ray distribution functions, of simplified electron range-energy relations, and neglected angular distributions. Nevertheless it made possible the calculation of cross sections for the inactivation of enzymes and viruses, and allowed extension to tracks in nuclear emulsions and other detectors and to biological cells. It set the pattern for models of observable effects in the matter through which the ion passed. Here we outline subsequent calculations of radial dose which make use of improved knowledge of the electron emission spectrum, the electron range-energy relation, the angular distribution, and some considerations of molecular excitation, of particular interest both close to the path of the ion and the outer limits of electron penetration. These are applied to the modeling of action cross sections for the inactivation of several strains of E-coli and B. subtilis spores where extensive measurements in the "thin-down" region have been made with heavy ion beams. Such calculations serve to test the radial dose calculations at the outer limit of electron
Liu, Yuan [Department of Physics, State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China); Ning, Chuangang, E-mail: ningcg@tsinghua.edu.cn [Department of Physics, State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)
2015-10-14
Recently, the development of photoelectron velocity map imaging makes it much easier to obtain the photoelectron angular distributions (PADs) experimentally. However, explanations of PADs are only qualitative in most cases, and very limited works have been reported on how to calculate PAD of anions. In the present work, we report a method using the density-functional-theory Kohn-Sham orbitals to calculate the photodetachment cross sections and the anisotropy parameter β. The spherical average over all random molecular orientation is calculated analytically. A program which can handle both the Gaussian type orbital and the Slater type orbital has been coded. The testing calculations on Li{sup −}, C{sup −}, O{sup −}, F{sup −}, CH{sup −}, OH{sup −}, NH{sub 2}{sup −}, O{sub 2}{sup −}, and S{sub 2}{sup −} show that our method is an efficient way to calculate the photodetachment cross section and anisotropy parameter β for anions, thus promising for large systems.
Calculation of photo-nuclear reaction cross sections for 16O
Arasoglu Ali
2015-01-01
Full Text Available 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 16O isotopes. Transmutation of 16O isotopes changes physical properties of nuclear fuel. Due to above explanations, it is very important to calculate photo-nuclear reaction cross sections of 16O. In this study; for (γ,p, (γ,np, (γ,n and (γ,2n reactions of 16O, 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.
Status of theories for calculations of production cross sections of long-lived radionuclides
The theories discussed in this paper are confined to those currently being used or considered for the calculation of activation cross sections. The theories are the same regardless of whether the activation product is long lived or short lived. However, the cross sections for the generation of long-lived radionuclides are more difficult or expensive to measure, hence there are fewer data available and the requirement on the predictive capability of the theories used is more stringent. It is clear from other papers presented in this meeting and the adjoining NEANDC specialists' meeting on activation cross sections that the nuclear theories of interest to this group are those used or needed in modern Hauser-Feshbach (H-F) codes with pre-equilibrium correction and gamma-ray cascades. The H-F formalism is indispensable due to the sensitivity of the calculated results, especially isomeric ratios, to the spins and parities of the discrete levels as well as to the spin distributions in the total and exciton level densities. Topics included in this paper are the optical model, gamma-ray strength function, total and exciton level-density theories, and the pre-compound model. In each subject, we describe the most commonly used theories first, followed by relatively new developments that are used in at least one model code or the promising theories that do not appear to require a large effort for incorporation into existing H-F codes. 14 refs
CI-RMBPT calculations of photoionization cross sections from quasi-continuum oscillator strengths
Savukov, I M
2014-01-01
Many applications are in need of accurate photoionization cross-sections, especially in the case of complex atoms. Configuration-interaction relativistic many-body perturbation theory (CI-RMBPT) that has been successful in predicting atomic energies, matrix elements between discrete states, and other properties is quite promising, but it has not been applied to photo-ionization problems owing to extra complications arising from continuum states. In this paper a method that will allow the conversion of discrete CI-(R)MPBT oscillator strengths (OS) to photo-ionization cross sections with minimal modifications of the codes is introduced and CI-RMBPT cross sections of Ne, Ar, Kr, Xe are calculated. A consistent agreement with experiment is found. RMBPT corrections are particularly significant for Ar, Kr, and Xe and improve agreement with experiment compared to the particle-hole CI method. The demonstrated conversion method can be applied to CI-RMBPT photo-ionization calculations for a large number of multi-valenc...
Nobre, G P A; Escher, J E; Thompson, I J; Dupuis, M; Terasaki, J; Engel, J
2010-01-01
A microscopic calculation of the reaction cross-section for nucleon-nucleus scattering has been performed by explicitly coupling the elastic channel to all particle-hole (p-h) excitation states in the target and to all one-nucleon pickup channels. The p-h states may be regarded as doorway states through which the flux flows to more complicated configurations, and subsequently to long-lived compound nucleus resonances. Target excitations for 40,48Ca, 58Ni, 90Zr and 144Sm were described in a QRPA framework using a Skyrme functional. Reaction cross sections calculated in this approach were compared to predictions of a fitted optical potential and to experimental data, reaching very good agreement. Couplings between inelastic states were found to be negligible, while the couplings to pickup channels contribute significantly. For the first time observed reaction cross-sections are completely accounted for by explicit channel coupling, for incident energies between 10 and 40 MeV.
Nuclear model calculations of activation cross sections for fusion reactor technology
Intense neutron fluxes within fusion reactors that are currently being designed will lead to the activation of structural components. To assess and minimize this radioactivity, nuclear cross sections are needed for neutrons with energies up to 20 MeV. We describe research performed for the International Atomic Energy Agency (IAEA) Coordinated Research Programme on activation cross sections for fusion reactor technology, which has selected certain high-priority reactions for both experimental and theoretical study. Using statistical model codes, we have investigated: (1) excitation function cross sections for radionuclide production in the reactions 94Mo(n,p)94Nb, 109Ag(n,2n)108mAg, 151Eu(n,2n)150mEu, 153Eu(n,2n)152g+m2Eu, 159Tb(n,2n)158Tb, 187Re(n,2n)186mRe, 179Hf(n,2n)178m2Hf, 193Ir(n,2n)192m2Ir; and (2) the systematical dependence of isomeric ratios on isomer spin and incident-energy. Using our calculated results for the excitation functions, along with calculations by other groups, the theoretical excitation functions have been normalized to experimental values at 14.5 MeV to produce evaluated excitation functions. These evaluations can be used within radiation transport and nuclide inventory codes to design and assess the environmental impact of fusion reactors. (orig.)
Density functional calculations of multiphonon capture cross sections at defects in semiconductors
Barmparis, Georgios D.; Puzyrev, Yevgeniy S.; Zhang, X.-G.; Pantelides, Sokrates T.
2014-03-01
The theory of electron capture cross sections by multiphonon processes in semiconductors has a long and controversial history. Here we present a comprehensive theory and describe its implementation for realistic calculations. The Born-Oppenheimer and the Frank-Condon approximations are employed. The transition probability of an incoming electron is written as a product of an instantaneous electronic transition in the initial defect configuration and the line shape function (LSF) that describes the multiphonon processes that lead to lattice relaxation. The electronic matrix elements are calculated using the Projector Augmented Wave (PAW) method which yields the true wave functions while still employing a plane-wave basis. The LSF is calculated by employing a Monte Carlo method and the real phonon modes of the defect, calculated using density functional theory in the PAW scheme. Initial results of the capture cross section for a prototype system, namely a triply hydrogenated vacancy in Si are presented. The results are relevant for modeling device degradation by hot electron effects. This work is supported in part by the Samsung Advanced Institute of Technology (SAIT)'s Global Research Outreach (GRO) Program and by the LDRD program at ORNL.
Cross sections needed for investigations into track phenomena and Monte-Carlo calculations
Investigations into basic radiation action mechanisms as well as into applied radiation transport problems (e.g. electron microscopy) greatly benefit from detailed computer simulations of charged particle track structures in matter. The first and in fact most important and most difficult step in any such calculation is the derivation of reliable cross sections for the most relevant interaction processes in the material(s) under consideration. The second step in radiation transport calculations is the testing of results or intermediate results for quantitative or qualitative consistency with other experimental or theoretical information (e.g. yields, backscatter factors). This paper discusses the types of the most important collision cross sections for studies on track phenomena by detailed Monte-Carlo calculations, the necessary accuracy of such data and various means of consistency checks of calculated results. This will be done mainly with examples taken from radiation physics as applied to dosimetric and biological problems (i.e. to gaseous and condensed targets). 12 references, 8 figures
Burnable poisons are extensively used by Light Water Reactor designers in order to preserve the fuel reactivity potential and increase the cycle length (without increasing the uranium enrichment). In the industrial two-steps (assembly 2D transport-core 3D diffusion) calculation schemes these heterogeneities yield to strong flux and cross-sections perturbations that have to be taken into account in the final 3D burn-up calculations. This paper presents the application of an enhanced cross-section interpolation model (implemented in the French CRONOS2 code) to LWR (highly poisoned) depleted core calculations. The principle is to use the absorbers (or actinide) concentrations as the new interpolation parameters instead of the standard local burnup/fluence parameters. It is shown by comparing the standard (burnup/fluence) and new (concentration) interpolation models and using the lattice transport code APOLLO2 as a numerical reference that reactivity and local reaction rate prediction of a 2x2 LWR assembly configuration (slab geometry) is significantly improved with the concentration interpolation model. Gains on reactivity and local power predictions (resp. more than 1000 pcm and 20 % discrepancy reduction compared to the reference APOLLO2 scheme) are obtained by using this model. In particular, when epithermal absorbers are inserted close to thermal poison the 'shadowing' ('screening') spectral effects occurring during control operations are much more correctly modeled by concentration parameters. Through this outstanding example it is highlighted that attention has to be paid to the choice of cross-section interpolation parameters (burnup 'indicator') in core calculations with few energy groups and variable geometries all along the irradiation cycle. Actually, this new model could be advantageously applied to steady-state and transient LWR heterogeneous core computational analysis dealing with strong spectral-history variations under
A new calculation formula of the nuclear cross-section of therapeutic protons
Waldemar Ulmer
2014-03-01
Full Text Available Purpose: We have previously developed for nuclear cross-sections of therapeutic protons a calculation model, which is founded on the collective model as well as a quantum mechanical many particle problem to derive the S matrix and transition probabilities. In this communication, we show that the resonances can be derived by shifted Gaussian functions, whereas the unspecific nuclear interaction compounds can be represented by an error function, which also provides the asymptotic behavior. Method: The energy shifts can be interpreted in terms of necessary domains of energy to excite typical nuclear processes. Thus the necessary formulas referring to previous calculations of nuclear cross-sections will be represented. The mass number AN determines the strong interaction range, i.e. RStrong = 1.2·10-13·AN1/3cm. The threshold energy ETh of the energy barrier is determined by the condition Estrong = ECoulomb. Results and Conclusion: A linear combination of Gaussians, which contain additional energy shifts, and an error function incorporate a possible representation of Fermi-Dirac statistics, which is applied here to nuclear excitations and reaction with release of secondary particles. The new calculation formula provides a better understanding of different types of resonances occurring in nuclear interactions with protons. The present study is mainly a continuation of published papers.1-3--------------------------------Cite this article as: Ulmer W. A new calculation formula of the nuclear cross-section of therapeutic protons. Int J Cancer Ther Oncol 2014; 2(2:020211. DOI: 10.14319/ijcto.0202.11
Method for calculation of global sensitivity indices for few-group cross-section-dependent problems
The variance based global sensitivity analysis technique is robust, has a wide range of applicability and provides accurate sensitivity information for most models. However, it requires input variables to be mutually independent. A modification to this technique that allows one to deal with input variables that are block-wise correlated and normally distributed is presented. The focus of this study is the application of the modified global sensitivity analysis technique to calculations of reactor parameters that are dependent on multigroup or few-group neutron cross-sections. The result of the sensitivity analysis is obtained in terms of the global sensitivity indices, which can be used for characterising the contribution of uncertainties from the input cross-sections or their groups to the uncertainty of the calculated reactor parameter. The main effort in this work, besides presenting the theoretical background, is in establishing a method for a practical numerical calculation of the global sensitivity indices. The implementation of the method involves the calculation of multi-dimensional integrals, which can be prohibitively expensive to compute. Numerical techniques specifically suited to the evaluation of multidimensional integrals namely Monte Carlo and sparse grids methods are used, and their efficiency is compared. The method is illustrated and tested on a two-group cross-section dependent problem. In all the cases considered the results obtained with sparse grids achieved much better accuracy while using a significantly smaller number of samples. This aspect is addressed in a mini-study and a preliminary explanation of the results obtained is given. (author)
A comparison of measured jet cross sections with QCD calculations for e sup + e sup - annihilation
Magnussen, N.; Bartel, W.; Felst, R.; Haidt, D.; Kado, H.; Knies, G.; Krehbiel, H.; Meinke, R.; Meyer, H.; Olsson, J.; Ramcke, R.; Schmidt, D.; Steffen, P. (Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany, F.R.)); Smolik, L.; Ambrus, K.; Bethke, S.; Dieckmann, A.; Eckerlin, G.; Elsen, E.; Heintze, J.; Hellenbrand, K.H.; Komamiya, S.; Krogh, J. v.; Rieseberg, H.; Schmitt, H. von der; Spitzer, J.; Wagner, A.; Zimmer, M. (Heidelberg Univ. (Germany, F.R.). Physikalisches Inst.); Allison, J.; Barlow, R.J.; Chrin, J.; Duerdoth, I.P.; Loebinger, F.K.; Macbeth, A.A.; Murphy, P.G.; Stephens, K. (Manchester Univ. (UK)); Bowdery, C.K.; Finch, A.J.; Foster, F.; Hughes, G.; Nye, J.M.; Walker, I.W. (Lancaster Univ. (UK)); Cartwright, S.L.; Clarke, D.; Marshall, R.; Middleton, R.P. (Rutherford Appleton Lab., Chilton (UK)); Greenshaw, T.; Hagemann, J.; Heinzelmann, G.; Kleinwort, C.; Kuhlen, M.; Naroska, B.; Ould-Saada, F.; Pitzl, D.D.; Schneekloth, U.; Weber, G. (Hamburg Univ. (Germany; JADE Collaboration
1991-01-01
The cross sections for 2-, 3- and 4-jet production have been determined with the JADE detector, sited on the e{sup +}e{sup -}-storage ring PETRA. Data at {radical}s=14, 22, 35 and 44 GeV were compared to two O({alpha}{sub s}{sup 2})QCD calculations. A first analysis was performed with uncorrected data using the O({alpha}{sub s}{sup 2}) 3-jet matrix element calculation of Ellis, Ross and Terrano and the Lund String Monte Carlo program. In a second analysis the calculation of Kramer and Lampe was compared to corrected data. Both approaches gave a poor description of the data when the square of the momentum transfer Q{sup 2}=s was used as the scale of the running coupling constant. The description improved when the renormalization scale was adjusted to the process studied. The data were used to fix the best renormalization scale. (orig.).
Calculated cross sections for neutron induced reactions on 19F and uncertainties of parameters
Nuclear model codes were used to calculate cross sections for neutron-induced reactions on 19F for incident energies from 2 to 20 MeV. The model parameters in the codes were adjusted to best reproduce experimental data and are given in this report. The calculated results are compared to measured data and the evaluated values of ENDF/B-V. The covariance matrix for several of the most sensitive model parameters is given based on the scatter of measured data around the theoretical curves and the long-range correlation error of measured data. The results of these calculations form the basis for the new ENDF/B-VI fluorine evaluation. 44 refs., 64 figs., 14 tabs
Cross sections for the proton-induced production of radionuclides (40 less than or equal to A less than or equal to 60) from natural titanium, iron, and nickel were measured for proton energies from 80 to 200 MeV. The experimental data were compared with calculations according to Blann's hybrid model of nuclear reactions and to the semiempirical formulas of Rudstam and of Silberberg and Tsao. Based mainly on the new excitation functions, the production rates of cosmogenic radionuclides in meteorites by primary galactic protons were calculated. Since the interaction of primary solar and galactic particles with meteorites can be described with accuracy, the model calculations allow for a quantitative estimate of the action of secondary particles in meteorites. A method of completely describing the production of cosmogenic nuclides in meteorites that takes into account all sources of production is proposed. 51 references
Filtered thermal neutron captured cross-sections measurements and decay heat calculations
Recently, a pure thermal neutron beam has been developed for neutron capture measurements based on the horizontal channel No.2 of the research reactor at the Nuclear Research Institute, Dalat. The original reactor neutron spectrum is transmitted through an optimal composition of Bi and Si single crystals for delivering a thermal neutron beam with Cadmium ratio (Rcd) of 420 and neutron flux (Φth) of 1.6x106 n/cm2.s. This thermal neutron beam has been applied for measurements of capture cross-sections for nuclide of 51V, 55Mn, 180Hf and 186W by the activation method relative to the standard reaction 197Au(n,g)198Au. In addition to the activities of neutron capture cross-sections measurements, the study on nuclear decay heat calculations has been also considered to be developed at the Institute. Some results on calculation procedure and decay heat values calculated with update nuclear database for 235U, 238U, 239Pu and 232Th are introduced in this report. (author)
Hamiltonian guiding center drift orbit calculation for toroidal plasmas of arbitrary cross section
A Hamiltonian guiding center drift orbit formalism is developed which permits the efficient calculation of particle trajectories in toroidal devices of arbitrary cross section with arbitrary plasma β. The magnetic field is assumed to be a small perturbation from a zero order toroidal equilibrium field possessing either axial or helical symmetry. The equilibrium field can be modelled analytically or obtained numerically from equilibrium codes. A numerical code based on the formalism is used to study particle orbits in circular and bean-shaped tokamak configurations
Döge, Stefan; Müller, Stefan; Morkel, Christoph; Gutsmiedl, Erwin; Geltenbort, Peter; Lauer, Thorsten; Fierlinger, Peter; Petry, Winfried; Böni, Peter
2015-01-01
We present scattering cross sections $\\sigma_\\text{scatt}$ of ultracold neutrons (UCN) in liquid deuterium at T = 20.6 K, as recently measured by means of a transmission experiment. The indispensable thorough raw data treatment procedure is explained. A calculation model for coherent and incoherent scattering in liquid deuterium in the hydrodynamic limit based on appropriate physical concepts is provided and shown to ?t the data well. The applicability of the incoherent approximation for UCN scattering in liquid deuterium was tested and found to deliver acceptable results.
Space charge calculations of elliptical cross-section electron pulses in PARMELA
Koltenbah, B E C
1999-01-01
The Boeing version of the PARMELA code has been modified to compute the space charge effects for electron pulses with highly elliptical transverse cross-sections. A dynamic gridding routine has been added to allow good resolution for pulses as they evolve in time. The results from calculations for the chicane buncher in the 1 kW visible FEL beam line at Boeing indicate that the old circular algorithm of the SCHEFF subroutine overestimates the emittance growth in the bend plane by 30-40%.
HATHOR - HAdronic Top and Heavy quarks crOss section calculatoR
Aliev, M.; Lacker, H.; Langenfeld, U.; Moch, S.; Uwer, P.; Wiedermann, M.
2011-04-01
We present a program to calculate the total cross section for top-quark pair production in hadronic collisions. The program takes into account recent theoretical developments such as approximate next-to-next-to-leading order perturbative QCD corrections and it allows for studies of the theoretical uncertainty by separate variations of the factorization and renormalization scales. In addition it offers the possibility to obtain the cross section as a function of the running top-quark mass. The program can also be applied to a hypothetical fourth quark family provided the QCD couplings are standard. Program summaryProgram title: Hathor Catalogue identifier: AEID_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEID_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU GPL 3 No. of lines in distributed program, including test data, etc.: 5405 No. of bytes in distributed program, including test data, etc.: 327 718 Distribution format: tar.gz Programming language: C++, Fortran, Java Computer: Standard PCs (x86, x86_64 processors) Operating system: Linux RAM: 256 MB Classification: 11.1 External routines: Interface to LHAPDF for the user's choice of parton distribution functions, see http://projects.hepforge.org/lhapdf/ Nature of problem: Computation of total cross section in perturbative QCD. Solution method: Numerical integration of hard parton cross section convoluted with parton distribution functions. Running time: A few seconds to a few minutes on standard desktop PCs or notebooks, depending on the chosen options.
In order to investigate some aspects of the 'Intermediate Resonance Approximation' developed by Goldstein and Cohen, comparative calculations have been made using this method together with more accurate methods. The latter are as follows: a) For homogeneous materials the slowing down equation is solved in the fundamental mode approximation with the computer programme SPENG. All cross sections are given point by point. Because the spectrum can be calculated for at most 2000 energy points, the energy regions where the resonances are accurately described are limited. Isolated resonances in the region 100 to 240 eV are studied for 238U/Fe and 238U/Fe/Na mixtures. In the regions 161 to 251 eV and 701 to 1000 eV, mixtures of 238U and Na are investigated. 239Pu/Na and 239Pu/238U/Na mixtures are studied in the region 161 to 251 eV. b) For heterogeneous compositions in slab geometry the integral transport equation is solved using the FLIS programme in 22 energy groups. Thus, only one resonance can be considered in each calculation. Two resonances are considered, namely those belonging to 238U at 190 and 937 eV. The compositions are lattices of 238U and Fe plates. The computer programme DORIX is used for the calculations using the Intermediate Resonance Approximation. Calculations of reaction rates and effective cross sections are made at 0, 300 and 1100 deg K for homogeneous media and at 300 deg K for heterogeneous media. The results are compared to those obtained by using the programmes SPENG and FLIS and using the narrow resonance approximation
Perturbative calculation of the cross section in double ionization by high-energy Compton scattering
Kaliman, Z. [Rijeka Univ., Dept. of Physics, Faculty of Arts and Sciences (Croatia); Pisk, K.; Suric, T. [Rudjer Boskovic Institute, Zagreb (Croatia)
2007-06-15
In this paper we investigate double ionization in high-energy Compton scattering from the He-atom including both the shake-off mechanism and a perturbative correction to that mechanism. The correction is calculated in second-order perturbation theory and includes Coulomb electron-electron interaction in addition to the correlation in the ground state of the He-atom. Our calculations for the ratio of double to single cross section cover the range from 30 to 300 keV of impact photon energy and explain the slow convergence of the ratio towards the asymptotic value. We have found that the ratio approaches the constant value within 10% at about 100 keV. Our results agree reasonably well with the existing experimental data.
Preliminary calculations of medium-energy fission cross sections and spectra
Nucleon-induced fission cross sections determined from a statistical preequilibrium model are used in conjunction with a new scission-point model of fission fragment mass, charge and excitation energy distributions to produce evaporation model calculations of particle and gamma spectra and multiplicities from fission. Comparisons are made to experiment for the 14.5-MeV neutron-induced fission of 238U. In addition, calculated particle and gamma spectra will be compared with the ENDF/B library for 2- and 5-MeV neutron-induced fission of 235U and 238U, respectively. Initial predictions for these same quantities for proton-induced fission reactions at energies up to 100 MeV will be presented and discussed. 6 refs., 3 figs
Calculations of the mass absorption cross sections for carbonaceous nanoparticles modeling soot
In this paper we use an atomistic model to calculate the mass specific absorption cross section coefficient (MAC) of carbonaceous particles of nanometer size. The carbonaceous particles are built numerically to reproduce most of the structural characteristics of typical primary nanoparticles that are agglomerated in soot emitted in the Troposphere from combustion sources. Our model is based on the knowledge of the atomic positions and polarizabilities inside the primary nanoparticles and is used to study the influence of these atomistic characteristics on the optical properties of these nanoparticles. The results indicate that the atomistic composition of the soot primary nanoparticles may have a sufficiently strong impact on the mass specific absorption cross section coefficient curves to allow detection of differences between nanoparticles by using UV–visible spectroscopic measurements, in a well-suited wavelength range, i.e., typically between 200 and 350 nm. In a more general way, our calculations show that MAC values as well as differences between MAC curves corresponding to different primary nanoparticles may strongly vary with wavelength. As a consequence, measurements at a given wavelength only are certainly not representative of the absorption properties of these nanoparticles and thus should be considered with caution. Moreover, our approach clearly shows significant differences with classical macroscopic electromagnetic theory when calculating the optical properties of realistic primary soot nanoparticles that, in fact, cannot be considered as homogeneous spherical particles due to the presence of defects in their atomistic structure. - Highlights: • We calculate the MAC curves of carbonaceous particles. • Relation between atomistic characteristics and MAC curves is characterized. • We show that MAC curves depend on the atomistic composition of the nanoparticles • Difference between nanoparticles may be characterized by spectroscopic
Calculation of neutron cross-sections in the unresolved resonance region by the Monte Carlo method
The Monte-Carlo method is used to produce neutron cross-sections and functions of the cross-section probabilities in the unresolved energy region and a corresponding Fortran programme (ONERS) is described. Using average resonance parameters, the code generates statistical distribution of level widths and spacing between resonance for S and P waves. Some neutron cross-sections for U238 and U235 are shown as examples
Classical trajectory calculations for anisotropy-dependent cross sections for He-N2 mixtures
The classical expressions for kinetic theory cross sections which are related to the Senftleben-Beenakker effect on viscosity, diffusion, conductivity and thermal diffusion are evaluated, in the temperature range 77.3-1100 K. The depolarised Rayleigh scattering and rotational-relaxation cross sections are also obtained. Comparisons with experiment show that the present values for these cross sections are 10-80% larger than the measurments. These consistent discrepancies suggest that this potential surface is too anisotropic. (author)
Shouping SHANG; Fangyuan ZHOU; Wei LIU
2009-01-01
Because there is a great demand of reinforce-ment and retrofitting of aged structures nationwide, as well as the rapid development of innovative building materials,the adoption of strengthening RC structures using new inorganic materials has become possible. High-performance ferrocement laminate (HPFL) is an effective method of strengthening concrete structure. High-performance ferrocement laminate is a new type of inorganic material with the advantages such as high strength, small contraction, good bonding properties, etc.This paper introduces the formula of cross-section bending capacity for strengthening concrete beams with HPEL. A comparative analysis of experimental data, as well as the calculation of diagonal section bearing capacity of concrete members, is given.
Ressell, M T; Bloom, S D; Griest, K; Mathews, G J; Resler, D A
1993-01-01
We present the results of detailed nuclear shell model calculations of the spin-dependent elastic cross section for neutralinos scattering from \\si29 and \\ge73. The calculations were performed in large model spaces which adequately describe the configuration mixing in these two nuclei. As tests of the computed nuclear wave functions, we have calculated several nuclear observables and compared them with the measured values and found good agreement. In the limit of zero momentum transfer, we find scattering matrix elements in agreement with previous estimates for \\si29 but significantly different than previous work for \\ge73. A modest quenching, in accord with shell model studies of other heavy nuclei, has been included to bring agreement between the measured and calculated values of the magnetic moment for \\ge73. Even with this quenching, the calculated scattering rate is roughly a factor of 2 higher than the best previous estimates; without quenching, the rate is a factor of 4 higher. This implies a higher se...
Cross Sections Calculations of ( d, t) Nuclear Reactions up to 50 MeV
Tel, E.; Yiğit, M.; Tanır, G.
2013-04-01
In nuclear fusion reactions two light atomic nuclei fuse together to form a heavier nucleus. Fusion power is the power generated by nuclear fusion processes. In contrast with fission power, the fusion reaction processes does not produce radioactive nuclides. The fusion will not produce CO2 or SO2. So the fusion energy will not contribute to environmental problems such as particulate pollution and excessive CO2 in the atmosphere. Fusion powered electricity generation was initially believed to be readily achievable, as fission power had been. However, the extreme requirements for continuous reactions and plasma containment led to projections being extended by several decades. In 2010, more than 60 years after the first attempts, commercial power production is still believed to be unlikely before 2050. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. In the fusion reactor, tritium self-sufficiency must be maintained for a commercial power plant. Therefore, for self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. Working out the systematics of ( d, t) nuclear reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at different energies. Since the experimental data of charged particle induced reactions are scarce, self-consistent calculation and analyses using nuclear theoretical models are very important. In this study, ( d, t) cross sections for target nuclei 19F, 50Cr, 54Fe, 58Ni, 75As, 89Y, 90Zr, 107Ag, 127I, 197Au and 238U have been investigated up to 50 MeV deuteron energy. The excitation functions for ( d, t) reactions have been calculated by pre-equilibrium reaction mechanism. Calculation results have been also compared with the available measurements in
Nagy, Tibor; Vikár, Anna; Lendvay, György, E-mail: lendvay.gyorgy@ttk.mta.hu [Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2., H-1117 Budapest (Hungary)
2016-01-07
The quasiclassical trajectory (QCT) method is an efficient and important tool for studying the dynamics of bimolecular reactions. In this method, the motion of the atoms is simulated classically, and the only quantum effect considered is that the initial vibrational states of reactant molecules are semiclassically quantized. A sensible expectation is that the initial ensemble of classical molecular states generated this way should be stationary, similarly to the quantum state it is supposed to represent. The most widely used method for sampling the vibrational phase space of polyatomic molecules is based on the normal mode approximation. In the present work, it is demonstrated that normal mode sampling provides a nonstationary ensemble even for a simple molecule like methane, because real potential energy surfaces are anharmonic in the reactant domain. The consequences were investigated for reaction CH{sub 4} + H → CH{sub 3} + H{sub 2} and its various isotopologs and were found to be dramatic. Reaction probabilities and cross sections obtained from QCT calculations oscillate periodically as a function of the initial distance of the colliding partners and the excitation functions are erratic. The reason is that in the nonstationary ensemble of initial states, the mean bond length of the breaking C–H bond oscillates in time with the frequency of the symmetric stretch mode. We propose a simple method, one-period averaging, in which reactivity parameters are calculated by averaging over an entire period of the mean C–H bond length oscillation, which removes the observed artifacts and provides the physically most reasonable reaction probabilities and cross sections when the initial conditions for QCT calculations are generated by normal mode sampling.
Nagy, Tibor; Vikár, Anna; Lendvay, György
2016-01-01
The quasiclassical trajectory (QCT) method is an efficient and important tool for studying the dynamics of bimolecular reactions. In this method, the motion of the atoms is simulated classically, and the only quantum effect considered is that the initial vibrational states of reactant molecules are semiclassically quantized. A sensible expectation is that the initial ensemble of classical molecular states generated this way should be stationary, similarly to the quantum state it is supposed to represent. The most widely used method for sampling the vibrational phase space of polyatomic molecules is based on the normal mode approximation. In the present work, it is demonstrated that normal mode sampling provides a nonstationary ensemble even for a simple molecule like methane, because real potential energy surfaces are anharmonic in the reactant domain. The consequences were investigated for reaction CH4 + H → CH3 + H2 and its various isotopologs and were found to be dramatic. Reaction probabilities and cross sections obtained from QCT calculations oscillate periodically as a function of the initial distance of the colliding partners and the excitation functions are erratic. The reason is that in the nonstationary ensemble of initial states, the mean bond length of the breaking C-H bond oscillates in time with the frequency of the symmetric stretch mode. We propose a simple method, one-period averaging, in which reactivity parameters are calculated by averaging over an entire period of the mean C-H bond length oscillation, which removes the observed artifacts and provides the physically most reasonable reaction probabilities and cross sections when the initial conditions for QCT calculations are generated by normal mode sampling. PMID:26747798
The quasiclassical trajectory (QCT) method is an efficient and important tool for studying the dynamics of bimolecular reactions. In this method, the motion of the atoms is simulated classically, and the only quantum effect considered is that the initial vibrational states of reactant molecules are semiclassically quantized. A sensible expectation is that the initial ensemble of classical molecular states generated this way should be stationary, similarly to the quantum state it is supposed to represent. The most widely used method for sampling the vibrational phase space of polyatomic molecules is based on the normal mode approximation. In the present work, it is demonstrated that normal mode sampling provides a nonstationary ensemble even for a simple molecule like methane, because real potential energy surfaces are anharmonic in the reactant domain. The consequences were investigated for reaction CH4 + H → CH3 + H2 and its various isotopologs and were found to be dramatic. Reaction probabilities and cross sections obtained from QCT calculations oscillate periodically as a function of the initial distance of the colliding partners and the excitation functions are erratic. The reason is that in the nonstationary ensemble of initial states, the mean bond length of the breaking C–H bond oscillates in time with the frequency of the symmetric stretch mode. We propose a simple method, one-period averaging, in which reactivity parameters are calculated by averaging over an entire period of the mean C–H bond length oscillation, which removes the observed artifacts and provides the physically most reasonable reaction probabilities and cross sections when the initial conditions for QCT calculations are generated by normal mode sampling
232Th and 238U neutron emission cross section calculations and analysis of experimental data
In this study, pre-equilibrium neutron-emission spectra produced by (n,xn) reactions on nuclei 232Th and 238U have been calculated. Angle-integrated cross sections in neutron induced reactions on targets 232Th and 238U have been calculated at the bombarding energies up to 18 MeV. We have investigated multiple pre-equilibrium matrix element constant from internal transition for 232Th (n,xn) neutron emission spectra. In the calculations, the geometry dependent hybrid model and the cascade exciton model including the effects of pre-equilibrium have been used. In addition, we have described how multiple pre-equilibrium emissions can be included in the Feshbach-Kerman-Koonin (FKK) fully quantum-mechanical theory. By analyzing (n,xn) reaction on 232Th and 238U, with the incident energy from 2 Me V to 18 Me V, the importance of multiple pre-equilibrium emission can be seen cleady. All calculated results have been compared with experimental data. The obtained results have been discussed and compared with the available experimental data and found agreement with each other
Program TOTELA calculating basic cross sections in intermediate energy region by using systematics
Program TOTELA can calculate neutron- and proton-induced total, elastic scattering and reaction cross sections and angular distribution of elastic scattering in the intermediate energy region from 20 MeV to 3 GeV. The TOTELA adopts the systematics modified from that by Pearlstein to reproduce the experimental data and LA150 evaluation better. The calculated results compared with experimental data and LA150 evaluation are shown in figures. The TOTELA results can reproduce those data almost well. The TOTELA was developed to fill the lack of experimental data of above quantities in the intermediate energy region and to use for production of JENDL High Energy File. In the case that there is no experimental data of above quantities, the optical model parameters can be fitted by using TOTELA results. From this point of view, it is also useful to compare the optical model calculation by using RIPL with TOTELA results, in order to verify the parameter quality. Input data of TOTELA is only atomic and mass numbers of incident particle and target nuclide and input/output file names. The output of TOTELA calculation is in ENDF-6 format used in the intermediate energy nuclear data files. It is easy to modify the main routine by users. Details are written in each subroutine and main routine
S-matrix approach calculation of the polarization contribution to the nucleosynthesis cross-section
In the framework of the S-matrix approach, the influence of the electric dipole polarizability of colliding particles upon the low-energy nucleosynthesis cross-section is estimated. It is shown that the relative contribution of the polarization effects to the reaction cross-section does not exceed the quantity of the order of 0.1%
Capture cross section and gamma-ray spectrum calculations for medium-weight nuclei
A double-peak, energy-dependent Breit-Wigner model of the E1 gamma-ray strength function was applied to nuclei from As to Rh, to predict their neutron capture cross sections and capture gamma-ray spectra. A consistent set of model parameters was obtained in this mass region to describe the step in the low-energy tail of the E1 strength function. This step allows agreement with photonuclear data at high energies, the correct GAMMA/sub gamma/ to be obtained for agreement with neutron capture cross-section data, and the calculation of the observed hardness in the capture gamma-ray spectra. For nuclei at or near the closed, N = 50 shell, however, the double-peak assumption breaks down. In these cases, good results are still obtained if the same set of model parameters is applied, except that the E1 strength function is formulated in terms of the first, narrower peak. 8 figures
ISICSoo: a class for the calculation of ionization cross sections from ECPSSR and PWBA theory
Batic, Matej; Cipolla, Sam J
2011-01-01
ISICS, originally a C language program for calculating K-, L- and M-shell ionization and X-ray production cross sections from ECPSSR and PWBA theory, has been reengineered into a C++ language class, named ISICSoo. The new software design enables the use of ISICS functionality in other software systems. The code, originally developed for Microsoft Windows operating systems, has been ported to Linux and Mac OS platforms to facilitate its use in a wider scientific environment. The reengineered software also includes some fixes to the original implementation, which ensure more robust computational results and a review of some physics parameters used in the computation. The paper describes the software design and the modifications to the implementation with respect to the previous version; it also documents the test process and provides some indications about the software performance.
Cross section calculations for subthreshold pion production in peripheral heavy-ion collisions
Norbury, J. W.; Cucinotta, F. A.; Deutchman, P. A.; Townsend, L. W.
1986-01-01
Total cross sections angular distributions, and spectral distributions for the exclusive production of charged and neutral subthreshold pions produced in peripheral nucleus-nucleus collisions are calculated by using a particle-hole formalism. The pions result from the formation and decay of an isobar giant resonance state formed in a C-12 nucleus. From considerations of angular momentum conservation and for the sake of providing a unique experimental signature, the other nucleus, chosen for this work to be C-12 also, is assumed to be excited to one of its isovector (1+) giant resonance states. The effects of nucleon recoil by the pion emission are included, and Pauli blocking and pion absorption effects are studied by varying the isobar width. Detailed comparisons with experimental subthreshold pion data for incident energies between 35 and 86 MeV/nucleon are made.
A computer programme which performs compound nucleus calculations using the Weisskopf-Ewing formalism is described. The programme will calculate the cross-sections for multi-particle emission by treating the process as a series of stages in the cascade. The relevant compound nucleus absorption cross-sections for particle channels are calculated with built-in optical model routines, and gamma ray emission is described by the giant dipole resonance formalism. Several choices for the final nucleus level density formula may be made using the level density routine contained in the programme. The total cross-section for the emission of a particle at any particular stage, is calculated together with the cross-section as a function of energy. The probability of leaving the final nucleus in a state of any particular energy is also obtained. (author)
Calculation of Gamma Displacement Cross Sections: Generation of Recoil Spectra from ENDF/B-VII
Radiation damage in materials is caused by the transfer of energy from an incident particle to the target atoms, which results in the redistribution of target atoms. During the nuclear reactor operation, various kinds of radiation are produced, including fast neutron, gamma, beta, high-energy ions etc. These radiations may affect the properties of reactor structural materials in a direct and/or indirect way. It is well known that fast neutrons have an effect on the degradation of materials. Whereas the impact of fast neutrons (En > 1 MeV) on material property changes is clearly recognized, the impact of gamma ray damage to materials is usually not significant. However, there has been some interest in gamma ray damage in metals in promoting accelerated embrittlement of reactor pressure vessel steels in the HFIR (High Flux Isotopes Reactor). In situations where there is a large water gap between pressure vessel and fuel assembly, gamma damage can become comparable to that produced by neutrons, on the basis of displacements per atom (dpa) parameter. A recent analysis of gamma ray displacement damage in the RPV of the General Electric Advanced Boiling Water Reactor (ABWR) indicated that the ratio of calculated gamma- to neutron-induced displacement damage rates is over 100% at the RPV inner diameter. Under a high gamma dose environment, embrittlement can be accelerated by radiation-enhanced mass transport mechanism. Because gamma rays are much more efficient than neutrons at producing freely-migrating defects, any radiation enhanced or induced processes that depend on the magnitude of defect fluxes to sinks, can be disproportionately affected by gamma. The direct evaluation of the contribution of gamma ray to damage in materials, quantified as a parameter of dpa, is made possible once the displacement damage cross section due to gamma rays are known. In this work, we present calculations for gamma ray displacement cross sections in various materials in the energy range
Approximation of few-group neutron cross-sections by functions of burnup and thermal-hydraulics parameters of a fuel cell is considered. The cross-section is written as a sum of two terms: the base cross-section, which depends only on burnup and is computed under the nominal reactor core conditions, and the deviation, which depends on burnup and thermal-hydraulics variables of the cell. A one-dimensional dependence of the base cross-section is interpolated by a cubic spline. Multi-dimensional dependencies of the deviation are approximated by a polynomial. Construction of the polynomial is performed by a best-fitting selection of the polynomial terms using the stepwise regression algorithm. The number of terms to satisfy a user-given accuracy of approximation is minimized. As an example, approximation of a set of two-group macro and micro cross-sections as functions of burnup, coolant and fuel temperature, coolant density and boron concentration is considered for a fuel pin cell of a VVER reactor. The constructed five-dimensional polynomial approximating cross-sections within 0.05% tolerance has about 20 terms for fast group cross-sections and 50 terms for thermal group cross-sections. The error of approximation is verified on the two data sets: the initial data used for approximation and the test data being computed on randomly selected points. Mean square and maximum errors are comparable for all the cross-sections for both sets of data. These results show that the initial data can be applied to control the approximation error
Calculation of the neutron-induced fission cross section of 233Pa
Since very recently, experimental data for the energy dependence of the 233Pa(n,f) cross section are finally available. This has stimulated a new, self-consistent cross section evaluation for the system n+233Pa in the incident neutron energy range 0.01-6 MeV. The results are quite different compared to earlier evaluation attempts. Since 233Pa is an important intermediary in the thorium based fuel cycle, its neutron reaction cross sections are key parameters in the modeling of future advanced reactor concepts
Calculations of cross sections for the synthesis of super-heavy nuclei in cold fusion reactions
The fusion cross sections are considered to be given by the product of three factors: the cross section to overcome the Coulomb barrier, the probability for the resulting system to reach the compound nucleus configuration by diffusion, and the probability for the compound nucleus to survive fission. The first and third factors are treated by more or less conventional equations, and the second by Brownian diffusion in one dimension. Adjusting one free parameter in the theory one can reproduce the twelve measured cross sections to within a factor of two. (author)
Cai, Xiao-Xiao; Llamas-Jansa, Isabel; Mullet, Steven;
2013-01-01
Geant4 is an open source general purpose simulation toolkit for particle transportation in matter. Since the extension of the thermal scattering model in Geant4.9.5 and the availability of the IAEA HP model cross section libraries, it is now possible to extend the application area of Geant4 to re...... models and the G4NDL library. However, cross sections of those missing isotopes were made available recently through the IAEA project “new evaluated neutron cross section libraries for Geant4”....
Kaganovich, I. D., Shnidman, Ariel, Mebane, Harrison, Davidson, R.C.
2008-10-10
Evaluation of ion-atom charge-changing cross sections is needed for many accelerator applications. A classical trajectory Monte Carlo (CTMC) simulation has been used to calculate ionization and charge exchange cross sections. For benchmarking purposes, an extensive study has been performed for the simple case of hydrogen and helium targets in collisions with various ions. Despite the fact that the simulation only accounts for classical mechanics, the calculations are comparable to experimental results for projectile velocities in the region corresponding to the vicinity of the maximum cross section. Shortcomings of the CTMC method for multielectron target atoms are discussed.
A calculation on n-D scattering cross sections in the energy range 0 to 20 MeV
A calculation on n-D scattering cross sections with phase shift analysis is carried out in the neutron energy range of 0 to 20 MeV. An optimum set of parameters are obtained by fitting the experimental data which include total, (n,2n) and differential cross section of n-D scattering. The comparisons were made between this calculated results and previous works. It was showed that the obtained differential elastic cross sections are in good agreement with the experimental values
Evaluation of ion-atom charge-changing cross sections is needed for many accelerator applications. A classical trajectory Monte Carlo (CTMC) simulation has been used to calculate ionization and charge exchange cross sections. For benchmarking purposes, an extensive study has been performed for the simple case of hydrogen and helium targets in collisions with various ions. Despite the fact that the simulation only accounts for classical mechanics, the calculations are comparable to experimental results for projectile velocities in the region corresponding to the vicinity of the maximum cross section. Shortcomings of the CTMC method for multielectron target atoms are discussed
Error Assessment of Homogenized Cross Sections Generation for Whole Core Neutronic Calculation
The objective of the work here was to assess the errors introduced by using 2D, few group homogenized cross sections to perform neutronic analysis of BWR problems with significant axial heterogeneities. The 3D method of characteristics code DeCART is used to generate 2-group assembly homogenized cross sections first using a conventional 2D lattice model and then using a full 3D solution of the assembly. A single BWR fuel assembly model based on an advanced BWR lattice design is used with a typical void distribution applied to the fuel channel coolant. This model is validated against an MCNP model. A comparison of the cross sections is performed for the assembly homogenized planar cross sections from the DeCART 3D and DeCART 2D solutions
A semi-empirical approach to the calculation of cross section functions (absolute value and energy dependence) for the electron-impact ionization of several neutral and ionized fullerenes C60n+ (n =0-3) was developed, for which reliable experimental data have been reported. In particular, it is proposed a modification of the simplistic assumption that the ionization cross section of a cluster/fullerene is given as the product of the monomer ionization cross section and a factor ma, where 'm' is the number of monomers in the ensemble and 'a' is a constant. A comparison between these calculations and the available experimental data reveals good agreement for n = 0,103. In the case of ionization of C602+ (n = 2) the calculation lies significantly below the measured cross section which it was interpret as an indication that additional indirect ionization processes are present for this charge state. (nevyjel)
Cross sections for electron and photon processes required by electron-transport calculations
Electron-transport calculations rely on a large collection of electron-atom and photon-atom cross-section data to represent the response characteristics of the target medium. These basic atomic-physics quantities, and certain qualities derived from them that are now commonly in use, are critically reviewed. Publications appearing after 1978 are not given consideration. Processes involving electron or photon energies less than 1 keV are ignored, while an attempt is made to exhaustively cover the remaining independent parameters and target possibilities. Cases for which data improvements can be made from existing information are identified. Ranges of parameters for which state-of-the-art data are not available are sought out, and recommendations for explicit measurements and/or calculations with presently available tools are presented. An attempt is made to identify the maturity of the atomic-physics data and to predict the possibilities for rapid changes in the quality of the data. Finally, weaknesses in the state-of-the-art atomic-physics data and in the conceptual usage of these data in the context of electron-transport theory are discussed. Brief attempts are made to weight the various aspects of these questions and to suggest possible remedies
Smith, L.A.; Gallmeier, F.X. [Oak Ridge Institute for Science and Energy, TN (United States); Gehin, J.C. [Oak Ridge National Lab., TN (United States)] [and others
1995-05-01
The FOEHN critical experiment was analyzed to validate the use of multigroup cross sections and Oak Ridge National Laboratory neutronics computer codes in the design of the Advanced Neutron Source. The ANSL-V 99-group master cross section library was used for all the calculations. Three different critical configurations were evaluated using the multigroup KENO Monte Carlo transport code, the multigroup DORT discrete ordinates transport code, and the multigroup diffusion theory code VENTURE. The simple configuration consists of only the fuel and control elements with the heavy water reflector. The intermediate configuration includes boron endplates at the upper and lower edges of the fuel element. The complex configuration includes both the boron endplates and components in the reflector. Cross sections were processed using modules from the AMPX system. Both 99-group and 20-group cross sections were created and used in two-dimensional models of the FOEHN experiment. KENO calculations were performed using both 99-group and 20-group cross sections. The DORT and VENTURE calculations were performed using 20-group cross sections. Because the simple and intermediate configurations are azimuthally symmetric, these configurations can be explicitly modeled in R-Z geometry. Since the reflector components cannot be modeled explicitly using the current versions of these codes, three reflector component homogenization schemes were developed and evaluated for the complex configuration. Power density distributions were calculated with KENO using 99-group cross sections and with DORT and VENTURE using 20-group cross sections. The average differences between the measured values and the values calculated with the different computer codes range from 2.45 to 5.74%. The maximum differences between the measured and calculated thermal flux values for the simple and intermediate configurations are {approx} 13%, while the average differences are < 8%.
We have analyzed differential cross sections (DCSs) for the elastic scattering of electrons by neutral atoms that have been derived from two commonly used atomic potentials: the Thomas-Fermi-Dirac (TFD) potential and the Dirac-Hartree-Fock (DHF) potential. DCSs from the latter potential are believed to be more accurate. We compared DCSs for six atoms (H, Al, Ni, Ag, Au, and Cm) at four energies (100, 500, 1000, and 10 000 eV) from two databases issued by the National Institute of Standards and Technology in which DCSs had been obtained from the TFD and DHF potentials. While the DCSs from the two potentials had similar shapes and magnitudes, there can be pronounced deviations (up to 70%) for small scattering angles for Al, Ag, Au, and Cm. In addition, there were differences of up to 400% at scattering angles for which there were deep minima in the DCSs; at other angles, the differences were typically less than 20%. The DCS differences decreased with increasing electron energy. DCSs calculated from the two potentials were compared with measured DCSs for six atoms (He, Ne, Ar, Kr, Xe, and Hg) at energies between 50 eV and 3 keV. For Ar, the atom for which experimental data are available over the largest energy range there is good agreement between the measured DCSs and those calculated from the TFD and DHF potentials at 2 and 3 keV, but the experimental DCSs agree better with the DCSs from the DHF potential at lower energies. A similar trend is found for the other atoms. At energies less than about 1 keV, there are increasing differences between the measured DCSs and the DCSs calculated from the DHF potential. These differences were attributed to the neglect of absorption and polarizability effects in the calculations. We compare transport cross sections for H, Al, Ni, Ag, Au, and Cm obtained from the DCSs for each potential. For energies between 200 eV and 1 keV, the largest differences are about 20% (for H, Au, and Cm); at higher energies, the differences are
Yield-weighted average cross sections of neutron radiative capture, (n,2n), and (n,3n) reactions over prompt fission products (FPs) from 235U and 239Pu are calculated. The prompt fission production yields are taken from the ENDF/B-VII.0 library. The FPs for each fissile material exist over a range of approximately 1000 neutron-rich nuclides. Several nuclear reaction codes are utilized for calculating the cross sections on each individual fission product - EMPIRE-2.19, TALYS-1.0, GNASH, and CoH. The influence of the FP isomers on the average cross sections is examined with TALYS. We investigate the dependence of the average cross sections on the number of FPs taken for averaging. It is shown that the average capture cross section is much more sensitive to the number of FPs included, compared with the (n,2n) and (n,3n) reactions. An intercomparison of the calculated cross sections with the different reaction codes is carried out. In the capture reaction, EMPIRE predicted lower cross section than TALYS and CoH owing to different default assumptions used in the γ-ray strength function modeling. Moreover, the pre-equilibrium models implemented in each code give different predictions for the neutron-emission reactions, although the differences are relatively small. We also discuss a difference between the macroscopic and microscopic calculation options in TALYS for the pre-equilibrium model, optical potential model, and γ-ray strength function. The predictive capability of the reaction codes for the capture reaction is examined by comparing their calculations with the ENDF data, which are based on measurements. Compared with the historic Foster and Arthur's evaluation, our new (n,2n) predictions are similar, although our capture predictions are almost an order of magnitude higher. Recommended cross sections for use in applications have been tabulated in ENDF-formatted files. (author)
Calculated cross sections for transport coefficients of H{sub 2} dilute in He and HI gas
Schaefer, J., E-mail: jas@mpa-garching.mpg.de [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Strasse 1, 85741 Garching (Germany)
2010-08-23
Graphical abstract: Transport coefficients of mixed gases like isotropic diffusion of hydrogen in helium gas are determined by relaxation cross sections model calculations in astrophysics: the three gas components H{sub 2}, HI, and He of the Waldmann-Snider theory. - Abstract: Relaxation cross sections determining transport coefficients of the binary systems He-H{sub 2} and HI-H{sub 2} have been calculated by using the Waldmann-Snider formalism of the linearized collision operator. After starting with the rotational relaxation times, which are determined by inelastic rotational transitions only, all the following contributions of relaxation cross sections to the binary transport coefficients of the viscosity, heat conductivity, and diffusion have been confined to the valid isotropic approximations, i.e. containing results of elastic collisions, which are only slightly corrected by inelastic effects. Cross sections of the pure gas components have not been done in this paper. The prepared input data have been differential cross sections of a sufficient number of energies and enough initial rotational j states of the molecules to produce converged results at temperatures from 5 K up to 1000 K. Convergence with regard to the contributed j states are shown in figures, the resulting numbers of the cross sections are printed in tables for temperatures up to 600 K. The results show almost identical cross sections for the ortho-H{sub 2} and para-H{sub 2} gas components in relaxation cross sections of purely translational motion, whereas cross sections pertaining purely internal rotational motion are significantly different for para-H{sub 2} and ortho-H{sub 2}, and cross sections pertaining coupling of rotational-translational motion could be shown to be negligible as demonstrated in figures.
Yu, Dong; Jiang, Lan; Wang, Feng; Qu, Liangti; Lu, Yongfeng
2016-05-01
Time-dependent density functional theory-based first-principles calculations have been used to study the ionization process and electron excitation. The results show that the number of excited electrons follows the power law σ k I k at peak intensities of I employing the calculated cross section value in the plasma model, the damage threshold fluences are theoretically estimated, being consistent with the experimental data, which validates the calculated value of multiphoton absorption cross section. The preliminary multiscale model shows great potential in the simulation of laser processing.
The improved adiabatic representation is used in calculations of elastic and hyperfine-transition cross sections for symmetric collisions of pμ, dμ, and tμ with bare p, d, and t nuclei and with H, D, and T atoms, respectively. The cross sections for dμ+d and tμ+t are in excellent agreement with other recent determinations, while those for pμ+p are about 30% larger at low energies. The electronic screening is calculated nonperturbatively and found to be about 30% smaller in magnitude than the previously calculated value at large internuclear distances, and to deviate considerably from the asymptotic form in the molecular region. The resulting screened elastic cross sections are up to 60% smaller than those obtained using the old screening potential. The reactance matrices, needed for calculations of molecular-target effects, are given in tables
FOURACES, MultiGroup Cross-Sections, Resonance Calculation from ENDF/B, KEDAK, UKNDL
1 - Description of problem or function: FOURACES produces spectrum weighted, group averaged nuclear cross sections and related parameters for nuclear reactor calculations. ENDF/B-IV, ENDF/B-V, KEDAK or UKNDL libraries may be used as basic input data. The weighting function and energy group structure are arbitrary, and are specified by the user. The code can deal with single or multi-level Breit-Wigner Adler- Adler and Reich-Moore resonance formalisms, and includes a Doppler broadening option. 4. Method of solution: If the weighting function is simple enough group averaged quantities are computed from the point data and interpolation rule read from the evaluated data library using analytic formulae. Otherwise the integrations are performed using the trapezium rule. Resonance data are converted into point data using subroutines written primarily for the program CRESO (abstract NEA 0719), then Doppler broadened, and finally group averaged. 5. Restrictions on the complexity of the problem: A maximum of 256 energy groups can be dealt with
Baryon + Baryon → (ΩΩ)Jπ=0+ +X Cross Section Calculation
YU You-Wen
2002-01-01
The cross sections ofΩ + Ξ→ (ΩΩ)Jπ=0+ + K(K*) and Ω + Ω→ (ΩΩ)Jπ 0+ + η(φ) are studied by using an effective Hamiltonian method.For the two pseudo-scalar meson production processes,the cross sections are still in the order of severalμbs,but for the two vector meson production processes,the cross sections are about 10 times larger than those in pseudo-scalar meson production case when the coupling constants of vector meson fields arefixed according to gNNp and fNNp in NN scattering and the SU(3) relation.
The program CORA was prepared on the basis of Hauser and Feshbach compound reaction formalism. It allows the differential cross-section distributions for the elastic and inelastic scattering of alpha particles (via compound nucleus state) to be calculated. The transmission coefficients are calculated on the basis of a four parameter optical model. The search procedure is also included. (author)
Calculation for electron impact total ionization cross sections on halogen compounds (BF, SiF, BCI, SiCl) are performed employing Spherical Complex Optical Potential and Complex Optical Potential - ionization contribution (CSP-ic) formalisms. In this article we are presenting data for energies ranging from above threshold to 2000 eV. Our results are compared with available experimental and theoretical data wherever available. It is found that the present result gives a better account of the ionization cross sections. (author)
Frolov, Alexei M.
2015-01-01
New approach to highly accurate calculations of the photodetachment cross-sections of the negatively charged hydrogen ions is developed. This effective, fast and numerically stable method is based on the use of the Rayleigh's formula for the spherical Bessel functions. Photodetachment cross-sections of the negatively charged hydrogen ion(s) ${}^{\\infty}$H$^{-}$, ${}^{1}$H$^{-}$ (protium), ${}^{2}$H$^{-}$ (deuterium D$^{-}$) and ${}^{3}$H$^{-}$ (tritium T$^{-}$) are determined with the use of ...
Investigation of dynamical effects in heavy-ion induced fusion reactions is an area of intense research. Much progress has been made in this field both on the theoretical and experimental front. In order to test this we have measured the fusion (Evaporation residue (ER)) cross-section for 16O+64Zn and 32S+48Ti systems. We report here the results on cross-section measurements and the comparison with the predictions of Time Dependent Hartree Fock (TDHF) calculations
The method of nuclear elastic scattering cross sections calculations has proposed for incident hadrons and complex particles within quasi-classic approximation using scattering phases. The calculation have performed for proton-nucleus elastic scattering cross sections from 182 MeV to 1 GeV. The calculating cross sections angular dependencies describe satisfactorily the experimental data behaviour in secondary maxima neighbourhood
Analytical formulas for calculation of K X-ray production cross sections by alpha ions
In the present study, different procedures are followed to deduce the semi-empirical and the empirical K X-rayX-ray production cross sections induced by alpha ions from the available experimental data and the theoretical results of the ECPSSR model for elements with 20≤Z≤30. The deduced K X-ray production cross sections are compared with predictions from ECPSSR model and with other earlier works. Generally, the deduced K X-ray production cross sections obtained by fitting the available experimental data for each element separately give the most reliable values than those obtained by a global fit. - Highlights: ► The results were presented for elements with atomic numbers 20≤Z≤30 by alpha impact. ► The present semi-empirical formulas were derived from both theoretical and experimental values. ► The available experimental data are directly fitted to deduce the empirical one. ► The results obtained for each element separately give the most reliable values than those obtained by a global fit. ► This procedure is proposed as a black-box way to quickly estimate the cross section.
Computer codes incorporating advanced nuclear models (optical, statistical and pre-equilibrium decay nuclear reaction models) were used to calculate neutron cross sections needed for fusion reactor technology. The elastic and inelastic scattering (n,2n), (n,p), (n,n'p), (n,d) and (n,γ) cross sections for stable molybdenum isotopes Mosup(92,94,95,96,97,98,100) and incident neutron energy from about 100 keV or a threshold to 20 MeV were calculated using the consistent set of input parameters. The hydrogen production cross section which determined the radiation damage in structural materials of fusion reactors can be simply deduced from the presented results. The more elaborated microscopic models of nuclear level density are required for high accuracy calculations
JIANG Jun; DONG Chen-Zhong; XIE Lu-You; WANG Jian-Guo; YAN Jun; Stephan Fritzsche
2007-01-01
A fully relativistic distorted-wave program is developed based on the Grasp92 and Ratip packages to calculate electron impact excitation (EIE) cross sections. As a first application of the program, the EIE cross sections of Be-like C2+ ions from the metastable ls22s2p 3P to 1s22p2 3P excitation and the inner-shell excitations are calculated systematically. Meanwhile, the correlation effects of target states are discussed. It is found that the correlation effects play an important role in the iow energy EIE cross sections. An excellent agreement is found when the results are compared with previous calculations and recent measurements.
239Pu(n,2n) 238Pu cross section inferred from IDA calculations and GEANIE measurements
Chen, H; Ormand, W E; Dietrich, F S
2000-09-01
This report presents the latest {sup 239}Pu(n,2n){sup 238}Pu cross sections inferred from calculations performed with the nuclear reaction-modeling code system, IDA, coupled with experimental measurements of partial {gamma}-ray cross sections for incident neutron energies ranging from 5.68 to 17.18 MeV. It is found that the inferred {sup 239}Pu(n,2n){sup 238}Pu cross section peaks at E{sub inc} {approx} 11.4 MeV with a peak value of approximately 326 mb. At E{sub inc} {approx} 14 MeV, the inferred {sup 239}Pu(n,2n){sup 238}Pu cross section is found to be in good agreement with previous radio-chemical measurements by Lockheed. However, the shape of the inferred {sup 239}Pu(n,2n){sup 238}Pu cross section differs significantly from previous evaluations of ENDL, ENDF/B-V and ENDF/B-VI. In our calculations, direct, preequilibrium, and compound reactions are included. Also considered in the modeling are fission and {gamma}-cascade processes in addition to particle emission. The main components of physics adopted and the parameters used in our calculations are discussed. Good agreement of the inferred {sup 239}Pu(n,2n){sup 238}Pu cross sections derived separately from IDA and GNASH calculations is shown. The two inferences provide an estimate of variations in the deduced {sup 239}Pu(n,2n){sup 238}Pu cross section originating from modeling.
Yousfi, M.; Robin-Jouan, P.; Kanzari, Z.
2008-05-01
The critical electric fields of hot SF6 are calculated for large temperature and pressure ranges (300 K to 3000 K from 1 bar to several bars). Calculations are based on a multi-term electron Boltzmann equation solution which needs the knowledge of electron-gas collision cross sections for ten SF6 dissociation products. The collision cross sections are fitted using an electron-swarm unfolding technique. These critical fields are then used to predict the circuit breaker behaviours during the SF6 recovery phase.
Effect of three cross-section libraries on the calculated neutron flux in the cavity of a PWR
The objective of this study was to compare calculations of pressure vessel surveillance dosimetry foil reaction rates computed using the ENDF/B-VI cross-section libraries for all reactor core and in-vessel materials except the reactor pressure vessel for which the ENDF/B-V, ENDF/B-VI, and LANL T-2 iron cross sections were substituted. Reaction rates for dosimetry foils in the cavity surrounding the pressure vessel of a pressurized water reactor were determined using the MCNP4A code. These calculations were compared to measured reaction rates from dosimetry foil experiments conducted during cycle 10 of Arkansas Nuclear One unit 1 (ANO-1)
The effect of errors in cross-section data on calculations for a large dilute fast reactor
The neutron physics of a large power fast reactor with a 1500 l core containing about 1000 kg of plutonium have been calculated using five-group diffusion theory. The effect on the critical size and breeding ratio of varying each cross-section in turn has been determined. The most important use of the results is to indicate the accuracy required for the cross-section data used in this type of calculation, but they can also be used to estimate the effect on the reactor of small changes in core composition or neutron spectrum. (author)
A program (RESQ) based on quadratures that evaluates, from ENDF/B data, the resolved resonance contribution in group-averaged cross sections (capture, fission and scattering) was developed. Single and Multilevel Breit-Wigner parameters are accepted. Constant weighting function and zero degree kelvin were considered. To assure convergence, different quadrature orders may be analysed. Results are compared with other codes' reconstruction and integration methods. (author)
Analytical calculation of the average scattering cross sections using fourier series
The precise determination of the Doppler broadening functions is very important in different applications of reactors physics, mainly in the processing of nuclear data. Analytical approximations are obtained in this paper for average scattering cross section using expansions in Fourier series, generating an approximation that is simple and precise. The results have shown to be satisfactory from the point-of-view of accuracy and do not depend on the type of resonance considered. (author)
Measurement and calculation of excitation cross sections and level ionization by electron impact
The experimental and theoretical study of the atomic structure in neutral noble gases is studied in this work. It mainly deals with the determination of total cross sections by electron impact and transition probabilities, including: Chapter 1: Theoretical introduction and the intermediate coupling description obtained for 420 levels of s, p and d configurations in neutral noble gases. Chapter 2: Experimental and theoretical values for electron collision cross sections are obtained for several levels of He, Ne, Ar and Kr. Our results as well as those available from existing bibliography are sumarized and compared. By means of an intermediate coupling treatment a number of regularities is found that provides us with some useful approximate semi empirical expressions. Chapter 3: Determination of lifetime and transition probabilities. Lifetime measurements are carried out by means of laser excitation and multichannel delayed coincidences technique. The experimental setup and electronics are also described. Chapter 4: Details the experimental setup developed for electron cross sections measurement by the optical method. The difficulties of this method and their treatment are also shown. (Author)
Arthur, E.D.; Young, P.G.
1977-01-01
A brief description of the preequilibrium-statistical model code GNASH is given. Features which make the code applicable to the calculation of cross sections induced by nucleons of energy 40 MeV or less are described. Finally, examples of calculations of neutron- and proton-induced reaction cross sections, activation cross sections, and secondary spectra made with global input parameters are given.
The features and the algorithm of the program to calculate adjoint neutron cross sections on the basis of the continuous energy neutron cross sections as well as energy and angular distributions are described. The calculated adjoint cross sections are intended for Monte Carlo investigation of the nonuniform adjoint Boltzmann equation. 16 refs
JIANG Min; FANG Zhen-Yun; SANG Wen-Long; GAO Fei
2006-01-01
@@ In the minimum electromagnetism coupling model of interaction between photon and electron (positron), we accurately calculate photon chain renormalized propagator and obtain the accurate result of differential cross section of Bhabha scattering with a photon chain renormalized propagator in quantum electrodynamics. The related radiative corrections are briefly reviewed and discussed.
The calculations of the total cross sections of hypertriton diffractive interaction with protons, carried out precisely and in the Glauber approximation in three cluster model show that this approximation is satisfactory only for rather small (within the limits of experimental errors) values of the hypertriton binding energy
Umar, A. S.; Oberacker, V. E.
2008-01-01
We present a fully microscopic study of the $^{16}$O+$^{208}$Pb fusion using the density-constrained time-dependent Hartree-Fock theory. The calculated fusion cross-sections are in good agreement with the experimental data for the entire energy range indicating that the incorporation of dynamical effects is crucial in describing heavy-ion fusion.
Ullmann, J. L.; Krticka, M.; Kawano, T.; Bredeweg, T. A.; Baramsai, B.; Couture, A.; Haight, R. C.; Jandel, M.; Mosby, S.; O'Donnell, J. M.; Rundberg, R. S.; Vieira, D. J.; Wilhelmy, J. B.; Becker, J. A.; Wu, C. Y.; Chyzh, A.
2015-10-01
Calculations of the neutron-capture cross section at low neutron energies (10 eV through 100's of keV) are very sensitive to the nuclear level density and radiative strength function. These quantities are often poorly known, especially for radioactive targets, and actual measurements of the capture cross section are usually required. An additional constraint on the calculation of the capture cross section is provided by measurements of the cascade gamma spectrum following neutron capture. Recent measurements of 234 , 236 , 238U(n, γ) emission spectra made using the DANCE 4 π BaF2 array at the Los Alamos Neutron Science Center will be presented. Calculations of gamma-ray spectra made using the DICEBOX code and of the capture cross section made using the CoH3 code will also be presented. These techniques may be also useful for calculations of more unstable nuclides. This work was performed with the support of the U.S. Department of Energy, National Nuclear Security Administration by Los Alamos National Security, LLC (Contract DE-AC52-06NA25396) and Lawrence Livermore National Security, LLC (Contract DE-AC52-07NA2734).
Bernnat, W.; Keinert, J.; Mattes, M. [Inst. for Nuclear Energy and Energy Systems, Univ. of Stuttgart, Stuttgart (Germany)
2004-03-01
For the calculation of neutron spectra in cold and super thermal sources scattering laws for a variety of liquid and solid cyrogenic materials were evaluated and prepared for use in deterministic and Monte Carlo transport calculations. For moderator materials like liquid and solid H{sub 2}O, liquid He, liquid D{sub 2}O, liquid and solid H{sub 2} and D{sub 2}, solid CH{sub 4} and structure materials such as Al, Bi, Pb, ZrHx, and graphite scattering law data and cross sections are available. The evaluated data were validated by comparison with measured cross sections and comparison of measured and calculated neutron spectra as far as available. Further applications are the calculation of production and transport and storing of ultra cold neutrons (UCN) in different UCN sources. The data structures of the evaluated data are prepared for the common S{sub N}-transport codes and the Monte Carlo Code MCNP. (orig.)
For the calculation of neutron spectra in cold and super thermal sources scattering laws for a variety of liquid and solid cyrogenic materials were evaluated and prepared for use in deterministic and Monte Carlo transport calculations. For moderator materials like liquid and solid H2O, liquid He, liquid D2O, liquid and solid H2 and D2, solid CH4 and structure materials such as Al, Bi, Pb, ZrHx, and graphite scattering law data and cross sections are available. The evaluated data were validated by comparison with measured cross sections and comparison of measured and calculated neutron spectra as far as available. Further applications are the calculation of production and transport and storing of ultra cold neutrons (UCN) in different UCN sources. The data structures of the evaluated data are prepared for the common SN-transport codes and the Monte Carlo Code MCNP. (orig.)
In this report we investigate the adequacy of the available 233U cross-section data for calculation of experimental critical systems. The 233U evaluations provided in two evaluated nuclear data libraries, the U.S. Data Bank [ENDF/B (Evaluated Nuclear Data Files)] and the Japanese Data Bank [JENDL (Japanese Evaluated Nuclear Data Library)] are examined. Calculations were performed for six thermal and ten fast experimental critical systems using the Sn transport XSDRNPM code. To verify the performance of the 233U cross-section data for nuclear criticality safety application in which the neutron energy spectrum is predominantly in the epithermal energy range, calculations of four numerical benchmark systems with energy spectra in the intermediate energy range were done. These calculations serve only as an indication of the difference in calculated results that may be expected when the two 233U cross-section evaluations are used for problems with neutron spectra in the intermediate energy range. Additionally, comparisons of experimental and calculated central fission rate ratios were also made. The study has suggested that an ad hoc 233U evaluation based on the JENDL library provides better overall results for both fast and thermal experimental critical systems
Leal, L.C.
1993-01-01
In this report we investigate the adequacy of the available {sup 233}U cross-section data for calculation of experimental critical systems. The {sup 233}U evaluations provided in two evaluated nuclear data libraries, the U. S. Data Bank [ENDF/B (Evaluated Nuclear Data Files)] and the Japanese Data Bank [JENDL (Japanese Evaluated Nuclear Data Library)] are examined. Calculations were performed for six thermal and ten fast experimental critical systems using the Sn transport XSDRNPM code. To verify the performance of the {sup 233}U cross-section data for nuclear criticality safety application in which the neutron energy spectrum is predominantly in the epithermal energy range, calculations of four numerical benchmark systems with energy spectra in the intermediate energy range were done. These calculations serve only as an indication of the difference in calculated results that may be expected when the two {sup 233}U cross-section evaluations are used for problems with neutron spectra in the intermediate energy range. Additionally, comparisons of experimental and calculated central fission rate ratios were also made. The study has suggested that an ad hoc {sup 233}U evaluation based on the JENDL library provides better overall results for both fast and thermal experimental critical systems.
Barghouty, A. F.
2014-01-01
Accurate estimates of electroncapture cross sections at energies relevant to the modeling of the transport, acceleration, and interaction of energetic neutral atoms (ENA) in space (approximately few MeV per nucleon) and especially for multi-electron ions must rely on detailed, but computationally expensive, quantum-mechanical description of the collision process. Kuang's semi-classical approach is an elegant and efficient way to arrive at these estimates. Motivated by ENA modeling efforts for apace applications, we shall briefly present this approach along with sample applications and report on current progress.
Measurements and model calculations of the 110Cd(n,#betta#)/sup 111m/Cd cross section
The cross section for the 110Cd(n,#betta#)/sup 111m/Cd reaction has been measured in the energy 0.14 to 1.5 MeV by means of activation. Both natural cadmium and 110Cd- and 111Cd-enriched samples were used in the measurements in order to distinguish the capture activation reaction from the 111Cd(n,n')/sup 111m/Cd reaction, which becomes involved due to the presence of 111Cd in the samples. Optical, statistical and gamma-ray cascade model calculations were performed in order to explain the energy dependence of the capture activation cross section
Formulas which are needed to calculate transmission coefficients for the adiabatic coupled-channel approximation method are described. In terms of these coefficients, nuclear absorption cross sections may be obtained. First, derivations are given of various cross sections for a system of coupled inelastic channels in terms of the S matrix. The adiabatic approximation method is discussed for a rotational band, and the dynamical nuclear S matrix is obtained from the S matrix for scattering from a static rotor. The formulas are valid for a spheroidal rotor, with or without an extra-core particle, which does not interact with the projectile but does provide angular momentum to the target
Perkasa, Y. S. [Department of Physics, Sunan Gunung Djati State Islamic University Bandung, Jl. A.H Nasution No. 105 Cibiru, Bandung (Indonesia); Waris, A., E-mail: awaris@fi.itb.ac.id; Kurniadi, R., E-mail: awaris@fi.itb.ac.id; Su' ud, Z., E-mail: awaris@fi.itb.ac.id [Nuclear Physics and Biophysics Research Division, Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesa No. 10 Bandung 40132 (Indonesia)
2014-09-30
Comparative studies of actinide and sub-actinide fission cross section calculation from MCNP6 and TALYS have been conducted. In this work, fission cross section resulted from MCNP6 prediction will be compared with result from TALYS calculation. MCNP6 with its event generator CEM03.03 and LAQGSM03.03 have been validated and verified for several intermediate and heavy nuclides fission reaction data and also has a good agreement with experimental data for fission reaction that induced by photons, pions, and nucleons at energy from several ten of MeV to about 1 TeV. The calculation that induced within TALYS will be focused mainly to several hundred MeV for actinide and sub-actinide nuclides and will be compared with MCNP6 code and several experimental data from other evaluator.
The weighted total cross-sections (WTCS) theory is used to calculate electron impact excitation, ionization and dissociation cross-sections and rate coefficients of OH, H2, OH+, H2+, OH- and H2- diatomic molecules in the temperature range 1500-15000 K. Calculations are performed for H2(X, B, C), OH(X, A, B), H2+(X), OH+(X, a, A, b, c), H2-(X) and OH-(X) electronic states for which Dunham coefficients are available. Rate coefficients are calculated from WTCS assuming Maxwellian energy distribution functions for electrons and heavy particles. One and 2 temperatures (θe and θg respectively for electron and heavy particles kinetic temperatures) results are presented and fitting parameters (a, b and c) are given for each reaction rate coefficient: k(θ) a(θb)exp(-c/θ). (authors)
We describe research performed for the International Atomic Energy Agency (IAEA) Coordinated Research Programme on activation cross sections for fusion reactor technology. Using the GNASH nuclear modeling code, we have investigated: (1) production cross sections of isomeric states, and isomer ratios, for the reactions 94Mo(n,p)94Nb, 109Ag(n,2n)108mAg, 151Eu(n,2n)150m Eu, 153Eu(n,2n)152g+m2Eu, 159Tb(n,2n)158Tb, 187Re(n,2n)186mRe, 179Hf(n,2n)178m2Hf, 193Ir(n,2n)192m2Ir; (2) systematical dependence of isomeric ratios on isomer spin and incident-energy; (3) preequilibrium spin effects on calculated isomer production; and (4) intercomparison and evaluation of nuclear model excitation functions of isomer production cross sections. (author). 16 refs, 8 figs, 1 tab
The energy deposited by a proton in a C60 molecule is calculated over a broad collision velocity range from 0.1 to 5 au, using the free-electron gas model of Lindhard and Winther (1964 Mat. Fys. Medd. K Dan. Vidensk. Selsk. 34) and the C60 electron density distribution calculated by Puska and Nieminen. The energy lost by the proton is maximum near 1.8 au collision velocity in contrast with the saturation found in the low-velocity regime, in the 0.25-0.5 au velocity range, by Kunert and Schmidt. From the impact parameter dependence we deduce the distributions of deposited energies, the averaged energy losses and the C60 electronic stopping cross sections. It is found that the C60 molecule behaves as a carbon foil giving very similar absolute stopping cross sections per atom. (author). Letter-to-the-editor
We have computed cross sections and asymmetry parameters for the outer- and inner-valence photoionization of ethane using the Schwinger variational method with Pade corrections. The calculated total cross section is found to be in rather good agreement with the available electron-impact and photoabsorption measurements. One-electron resonant processes in the (1eg)-1 (3a1g)-1, and (2a1g)-1 ionization channels were examined comparing resonant states predicted from the virtual orbitals of a minimum basis set self-consistent-field (MBS-SCF) calculations with scattering resonances found using a local model potential for the electron-molecule interaction. The analysis of the interaction potential in terms of adiabatic radial components provides a description of the mechanism of the resonant trapping
Calculation and analysis of cross-sections for p+184W reactions up to 200 MeV
Sun, Jian-Ping; Zhang, Zheng-Jun; Han, Yin-Lu
2015-08-01
A set of optimal proton optical potential parameters for p+ 184W reactions are obtained at incident proton energy up to 250 MeV. Based on these parameters, the reaction cross-sections, elastic scattering angular distributions, energy spectra and double differential cross sections of proton-induced reactions on 184W are calculated and analyzed by using theoretical models which integrate the optical model, distorted Born wave approximation theory, intra-nuclear cascade model, exciton model, Hauser-Feshbach theory and evaporation model. The calculated results are compared with existing experimental data and good agreement is achieved. Supported by National Basic Research Program of China, Technology Research of Accelerator Driven Sub-critical System for Nuclear Waste Transmutation (2007CB209903) and Strategic Priority Research Program of Chinese Academy of Sciences, Thorium Molten Salt Reactor Nuclear Energy System (XDA02010100)
The multiconfiguration Hartree-Fock method for continuum wave functions has been used to calculate the scattering length and phase shifts over extremely low energies ranging from 0 to 1 eV very accurately for electron-helium scattering. The scattering length is calculated very accurately with wave functions computed exactly at zero energy, resulting in an upper bound of 1.1784. The electron correlation and polarization of the target by the scattering electron, which are very important in these calculations, have been taken into account in an accurate ab initio manner through the configuration-interaction procedure by optimizing both bound and continuum orbitals simultaneously at each kinetic energy of the scattered electron. Detailed results for scattering length, differential, total, and momentum-transfer cross sections obtained from the phase shifts are presented. The present scattering length is found to be in excellent agreement with the experimental result of Andrick and Bitsch [J. Phys. B 8, 402 (1975)] and the theoretical result of O'Malley, Burke, and Berrington [J. Phys. B 12, 953 (1979)]. There is excellent agreement between the present total cross sections and the corresponding experimental measurements of Buckman and Lohmann [J. Phys. B 19, 2547 (1986)]. The present momentum-transfer cross sections also show remarkable agreement with the experimental results of Crompton, Elford, and Robertson [Aust. J. Phys. 23, 667 (1970)
Wu Xing-Ju; Chen Xiang-Jun; Shan Xu; Chen Li-Qing; Xu Ke-Zun
2004-01-01
The triple differential cross section for the low-energy electron impact ionization of inner-valence 3s orbital of argon has been calculated using the modified distorted wave Born approximation in coplanar symmetric energy-sharing geometry. Satisfactory agreement between theory and experiment is achieved when the polarization and post-collisional interaction (PCI) are included in the calculations. It is shown that the polarization and PCI effects play a very important role in the case of argon at low incident energies.
Calculation of Double-Differential Cross Sections of n+7Li Reactions Below 20 MeV
ZHANG Jing-Shang; HAN Ying-Lu
2002-01-01
A new reaction model for light nuclei is proposed to analyze the measured data,especially for analysis of the double-differential cross sections of the outgoing particles.Many channels arc opened in the n + 7Li reaction below En＜ 20 MeV.The reaction mechanism is very complex,beside the sequential emissions there are also three-body breakup processes.Because of a strong recoil effect of light nucleus reactions,the energy balance is strictly taken into account.The comparisons of the calculated results with the double-differential measurements indicate that the model calculations are successful for the total outgoing neutrons.
Diez de la Obra, Carlos Javier; Stankovskiy, Alexey; Malambu, E.; Zerovnik, Gasper; Schillebeeckx, Peter; Van Den Eynde, Gert; Heyse, Jan; Cabellos de Francisco, Oscar Luis
2013-01-01
A review of the experimental data for natC(n,c) and 12C(n,c) was made to identify the origin of the natC capture cross sections included in evaluated data libraries and to clarify differences observed in neutronic calculations for graphite moderated reactors using different libraries. The performance of the JEFF-3.1.2 and ENDF/B-VII.1 libraries was verified by comparing results of criticality calculations with experimental results obtained for the BR1 reactor. This reactor is an air-cooled re...
钟晨; 蔡翔舟; 沈文庆; 张虎勇; 魏义彬; 陈金根; 马余刚; 郭威; 方德清
2003-01-01
The Boltzmann-Uehling-Uhlenbeck (BUU) model, which includes the Fermi motion, the mean field, individual nucleon-nucleon (N-N) interactions and the Pauli blocking effect, etc., is used to calculate the total reaction cross section σR induced by α-particles on different targets in the incident energy range from 17.4 to 48.1 MeV/u. The calculation result can well reproduce the experimental data. The nucleus-nucleus interaction radius parameterγ0 was extracted from experimental σR. It is found that γ0 becomes constant with the increasing mass number of target.
The one-dimension SN method code ANISN and specific cross section library ZPR-22 have been used to perform the design calculation of dose rate distribution along the radial and axial direction of HWZPR shielding. Through multi-case calculations and optimization analysis works, a double slab cover structure is adopted. It is combined with the feasibility of structure and the possibility of boron concentration to be merged in paraffin for design case. The calculation results of axial direction: the core lattice distance is 18 cm; core radius R = 113 cm; reflector saving of radial direction is 25 cm; transfer leakage Dy = Dz = 244.6 cm. The calculation results of radial direction; the core lattice distance is 18 cm; critical water level 138.5 cm; reflector saving of axial direction is 20 cm; transfer leakage correction parameter Dy = 160 cm
Ismail, M.; Ramadan, Kh.A. [Physics Department, Faculty of Science, Cairo University, Giza (Egypt)
2000-10-01
The heavy-ion (HI) potential between spherical and deformed nuclei is derived using an M3Y-type nucleon-nucleon (NN) interaction. The calculation of the exchange part of the HI potential was improved by using a finite-range NN exchange force instead of the zero-range pseudo-potential which is usually used in deriving the potential between deformed nuclei. We consider an {sup 154}Sm-{sup 16}O nuclear pair as an example to show the effect of finite range on the nucleus-nucleus potential for different deformation parameters and at different orientation angles of the deformed target nucleus. We calculated the fusion cross section and the barrier distribution in the WKB approximation and studied their dependence on the orientation and deformation of the target nucleus. The variations found due to improving the exchange part enhance the fusion cross section below the Coulomb barrier by a factor of about four. It has been found that both the cross section and the barrier distribution are very sensitive to the deformation parameters at energies below the Coulomb barrier. (author)
This paper presents the quantification of resonance interference effect for multi-group effective cross-section in lattice physics calculation. In the resonance self-shielding method based on the equivalence theory, the resonance interference effect among multiple nuclides cannot be treated directly to the multi-group effective cross-section. The continuous energy or the ultra-fine-group treatment can directly consider the effect, but the application to the fuel assembly geometry is not realistic with practical computation time. In the present study, the resonance interference effect to the multi-group effective cross-section is simply quantified by the resonance interference factor (RIF) in order to confirm the benefit for considering the effect. The RIF is generated for the typical pin-cell geometry of water moderated system. The multi-group effective cross-sections with and without RIFs are compared with the continuous energy Monte-Carlo result. As a result, the significant impact for considering the resonance interference effect is confirmed to the limited nuclide, reaction type and energy group. Fortunately, these have small effect on k-infinity because the resonance interference effect is mainly induced by the wide resonances of 238U to the other minor nuclides (e.g., 235U, 239Pu) in the limited resonance energy ranges. The results also show that the effect is small to the absorption cross-section of 238U, which is the dominant resonance nuclide in the fuel. The quantification results in the present study indicate a useful material to investigate the more advanced resonance treatment for the next generation lattice physics code. (author)
Minnesota Department of Natural Resources — FEMA Cross Sections are required for any Digital Flood Insurance Rate Map database where cross sections are shown on the Flood Insurance Rate Map (FIRM). Normally...
In a previous publication (ATOMIC DATA AND NUCLEAR DATA TABLES75, 1 (2000)), we gave seven-parameter analytical fits to theoretical reaction rates derived from nuclear cross sections calculated in the statistical model (Hauser-Feshbach formalism) for targets with 10≤Z≤83 (Ne to Bi) and for a mass range reaching the neutron and proton driplines. Reactions considered were (n,γ), (n,p), (n,α), (p,γ), (p,α), (α,γ), and their inverse reactions. Here, we present the theoretical nuclear cross sections and astrophysical reaction rates from which those rate fits were derived, and we provide these data as on-line electronic files. Corresponding to the fitted rates, two complete data sets are provided, one of which includes a phenomenological treatment of shell quenching for neutron-rich nuclei
Kaplan Abdullah
2015-01-01
Full Text Available Implementation of projects of new generation nuclear power plants requires the solving of material science and technological issues in developing of reactor materials. Melts of heavy metals (Pb, Bi and Pb-Bi due to their nuclear and thermophysical properties, are the candidate coolants for fast reactors and accelerator-driven systems (ADS. In this study, α, γ, p, n and 3He induced fission cross section calculations for 209Bi target nucleus at high-energy regions for (α,f, (γ,f, (p,f, (n,f and (3He,f reactions have been investigated using different fission reaction models. Mamdouh Table, Sierk, Rotating Liquid Drop and Fission Path models of theoretical fission barriers of TALYS 1.6 code have been used for the fission cross section calculations. The calculated results have been compared with the experimental data taken from the EXFOR database. TALYS 1.6 Sierk model calculations exhibit generally good agreement with the experimental measurements for all reactions used in this study.
WU Yong; YAN Bing; LIU Ling; WANG Jian-Guo
2007-01-01
The single charge transfer process in 3 He2+ + 4He collisions is investigated using the quantum-mechanical molecularorbital close-coupling method, in which the adiabatic potentials and radial couplings are calculated by using the ab initio multireference single- and double-excitation configuration interaction methods. The differential cross sections for the single charge transfer are presented at the laboratorial energies E = 6kev and 10keV for the projectile 3He2+. Comparison with the existing data shows that the present results are better in agreement with the experimental measurements than other calculations in the dominant small angle scattering, which is attributed to the accurate calculations of the adiabatic potentials and the radial couplings.
Chi Bao-Qian; Liu Ling; Wang Jian-Guo
2008-01-01
The non-dissociative charge-transfer processes in collisions between O3+ and H2 are investigated by using the quantum-mechanical molecular-orbital coupled-channel (QMOCC) method. The adiabatic potentials and radial cou-pling matrix elements.utilized in the QMOCC calculations are obtained with the spin-coupled valence-bond approach. Electronic and vibrational state-selective differential cross sections are presented for projectile energies of 0.1, 1.0 and 10.0 eV/u in the H2 orientation angles of 45° and 89°. The electronic and the vibrational state-selective differential cross sections show similar behaviours: they decrease as the scattering angle increases, and beyond a specific angle the oscillating structures appear. Moreover, it is also found that the vibrational state-selective differential cross sections are strongly orientation-dependent, which provides a possibility to determine the orientations of molecule H2 by identifying the vibrational state-selective differential scattering processes.
Calculated neutron-induced cross sections for 52Cr from 1 to 20 MeV and comparisons with experiments
Nuclear model codes were used to compute cross sections for neutron-induced reactions on 52Cr for incident energies from 1 to 20 MeV. The input parameters for the model codes were determined through analysis of experimental data in this energy region. Discussion of the models used, the input data, the resulting calculations, extensive comparisons to measured data, and comparisons to the Evaluated Nuclear Data File (ENDF/B-V) for Cr (MAT 1324) are included in this report. 103 refs., 67 figs., 12 tabs
Verification of a Multi-group Cross Section Library for Burnup Calculation
Daing, Aung Tharn; Kim, Myung Hyun [Kyung Hee Univ., Yongin (Korea, Republic of); Joo, Hang Yu [Seoul National Univ., Seoul (Korea, Republic of)
2013-05-15
Despite satisfying the estimation of the neutronic parameters without depletion to some extent, it still requires detailed investigation of the behavior of a fuel with strong neutron absorber over its operating life time by nTRACER, the direct whole core calculation code with the conventional semi Predictor-Corrector method. This study is mainly focused on the verification of the newly generated multi-group library for burnup calculation by nTRACER through the analysis of its performance of depletion calculation of UO{sub 2} fuel with strong neutron absorbers such as Gadolinium. Firstly, the depletion calculation results of nTRACER are presented by comparing the evolution of k-inf and the inventories of commonly found important isotopes as a function of burnup in the cases of gadolinia(GAD)-bearing fuel pin and fuel assembly (FA) with those of MCNPX-version.2.6.0. The newly generated multi-group library for burnup calculation by nTRACER was verified through GAD-bearing fuel after the new approach of resonance treatment had been employed. Though very good agreement in the overall effect reflected on the multiplication factor of FA at BOC, the evolution of k-inf along fuel irradiation history was systematically well underestimated by nTRACER when compared to Monte Carlo results.
ZZ UKCTR-1, Cross-Section Library for Neutron Flux and Neutron Reaction Rates in CTR Calculation
1 - Description of problem or function: Format: ANISN, DOT, MORSE, SWANLAKE; Number of Groups: 46 energy group structure from 14.2 MeV to 1 MeV; Nuclides: Li-6, Li-7, O, Be, Pb, Nb, Fe, Ni, Cr, Zr, V, Ti, H, D, T, C, Al, B-10, B-11, Cu-63, Cu-65, F, Na, K, Mo. Origin: UKNDL; Weighting Spectrum: 1/(Sigma t (E).E) weighting is used for groups 1 to 44 with Maxwellian weighting for the two thermal groups. UKCTR1 is a data library of neutron cross sections for 25 materials in a 46 energy group structure from 14.2 MeV to 1 MeV. It is designed for calculation of neutron fluxes and reaction rates in controlled thermonuclear reactors. The energy group structure is fine at 14 MeV and there are two thermal groups; the lethargy interval width per energy group for decreasing energy is as follows: 0.014, 0.036, 2 x 0.15, 15 x 0.3, 25 x 0.5, 2.935 and 3.091. Reaction cross sections including partial inelastic data are provided for the following materials: Li-6, Li-7, O, Be, Pb, Nb, Fe, Ni, Cr, Zr, V, Ti, H, D, T, C, Al, B-10, B-11, Cu-63, Cu-65, F, Na, K, Mo. 1/(Sigma t (E).E) weighting is used for groups 1 to 44 with Maxwellian weighting for the two thermal groups. Anisotropy of scattering is represented by a P order up to 4 (usually 0 to 4). Data for hydrogen and deuterium both in water and heavy water and in the gaseous state is available. As a supplement, neutron kerma factors are included for each of the nuclides in the library as well as 98 activation cross sections of importance in fusion reactor work. (These 98 activation cross sections have been extracted from the bulk of the UKCTR-I library to be in a more convenient form for programs such as ANISN.) The kerma factors were computed using the code ENBAL2, a revised version of ENBAL, which calculates multigroup kerma factors directly from multigroup cross sections together with reaction Q-values. This approach allows neutron heating calculations to be performed consistently with the flux calculation. 2 - Method of
The background cross section method for calculating the epithermal neutron spectra
We have developed a new methodology to the multigroup constants calculations, for thermal and fast reactors. The method to obtain the constants is extremely fast and simple, and it avoid repeated computations of the detailed neutron spectrum for different cell configurations (composition, geometry and temperature). (author)
The computer code, POD, was developed to calculate angle-differential cross sections and analyzing powers for shape-elastic scattering for collisions of neutron or light ions with target nucleus. The cross sections are computed with the optical model. Angle-differential cross sections for neutron inelastic scattering can also be calculated with the distorted-wave Born approximation. The optical model potential parameters are the most essential inputs for those model computations. In this program, the cross sections and analyzing powers are obtained by using the existing local or global parameters. The parameters can also be inputted by users. In this report, the theoretical formulas, the computational methods, and the input parameters are explained. The sample inputs and outputs are also presented. (author)
XCOM: Photon Cross Sections Database
SRD 8 XCOM: Photon Cross Sections Database (Web, free access) A web database is provided which can be used to calculate photon cross sections for scattering, photoelectric absorption and pair production, as well as total attenuation coefficients, for any element, compound or mixture (Z <= 100) at energies from 1 keV to 100 GeV.
Cross Sections and Lorentz Violation
Colladay, Don; Kostelecky, Alan
2001-01-01
The derivation of cross sections and decay rates in the Lorentz-violating standard-model extension is discussed. General features of the physics are described, and some conceptual and calculational issues are addressed. As an illustrative example, the cross section for the specific process of electron-positron pair annihilation into two photons is obtained.
Full text: The implementation in the reaction code system EMPIRE-2.19 of an advanced formalism for fission cross-section calculation has been completed. The formalism is based on the optical model for fission and can be applied for nuclei exhibiting double- or triple-humped barrier starting from sub-barrier excitation energies. The optical model for fission, initially developed to describe the resonant structure of the fission cross section at sub-barrier excitation energies due to the vibrational states in the second well of a double-humped fission barrier, was extended to light actinides by including the relations for the transmission coefficients through a complex triple-humped fission barrier. The real part of the fission barrier is parameterised as a function of the nucleus deformation by five smoothly joined parabolas. The imaginary potential is introduced only in the deformation range corresponding to the second well because the tertiary well is supposed to be shallow enough to neglect the damping of class III vibrational states. The transition states are assumed to be rotational states built on vibrational or non-collective band-heads. As the excitation energy increases, the shell effect, which causes the splitting of the outer barrier, diminishes and the outer humps lump into a single one. Therefore, in the present formalism, triple-humped barriers are associated only to the discrete transition states; the contribution of continuum to the fission coefficients is calculated considering a double-humped barrier. The parameters of the second single barrier equivalent with the outer humps are being determined from the condition of equal transmission coefficients. The saddle-point transition states in continuum are described by level densities (BCS below the critical energy and a modified version of Fermi Gas above) accounting for collective enhancements specific to the nuclear shape asymmetry at each saddle point . The neutron cross sections of 232Th in the
Electron transport calculations in warm dense matter using scattering cross sections
Burrill, D J; Charest, M R J; Starrett, C E
2015-01-01
The Ziman formulation of electrical conductivity is tested in warm and hot dense matter using the pseudo-atom molecular dynamics method. Several implementation options that have been widely used in the literature are systematically tested through a comparison to accurate but expensive Kohn-Sham density functional theory molecular dynamics (KS-DFT-MD) calculations. The comparison is made for several elements and mixtures and for a wide range of temperatures and densities, and reveals a preferred method that generally gives very good agreement with the KSDFT-MD results, but at a fraction of the computational cost.
On how sensitive the cross-section sensitivity calculations are to PN order approximations
In the mathematical expression of the nuclear data sensitivity function as derived from the first order perturbation theory both the angular fluxes and their expansion in the Legendre flux moments are required. Both terms are calculated by the traditional discrete ordinates transport codes and stored in the files. This leaves the developers of the nuclear data sensitivity and uncertainty codes several possible choices of the method to account for the neutron flux anisotropy. Three possibilities available in the SUSD3D code were studied here and compared using the FLATTOP-Pu benchmark exercise. This benchmark was particularly suitable due to its high flux anisotropy. (author)
Shizgal, Bernie D.
2016-08-01
Nonclassical quadratures based on a new set of half-range polynomials, Tn(x) , orthogonal with respect to w(x) =e - x - b /√{ x } for x ∈ [ 0 , ∞) are employed in the efficient calculation of the nuclear fusion reaction rate coefficients from cross section data. The parameter b = B /√{kB T } in the weight function is temperature dependent and B is the Gamow factor. The polynomials Tn(x) satisfy a three term recurrence relation defined by two sets of recurrence coefficients, αn and βn. These recurrence coefficients define in turn the tridiagonal Jacobi matrix whose eigenvalues are the quadrature points and the weights are calculated from the first components of the eigenfunctions. For nonresonant nuclear reactions for which the astrophysical function can be expressed as a lower order polynomial in the relative energy, the convergence of the thermal average of the reactive cross section with this nonclassical quadrature is extremely rapid requiring in many cases 2-4 quadrature points. The results are compared with other libraries of nuclear reaction rate coefficient data reported in the literature.
Theoretical calculation of photoionization cross sections of B-like ions: N2+,O3+ and F4+
Wang Guo-Li; Zhou Xiao-Xin
2009-01-01
There can be found some notable discrepancies with regard to the resonance structures when R-matrix calculations from the Opacity Project and other sources are compared with recent absolute experimental measurements of Bizau et al [Astron. Astrophts. 439 387 (2005)] for B-like ions N2+,03+ and F4+. We performed close-coupling calculatious based on the R-matrix formalism for the photoionizations of ions mentioned above both for the ground states and first excited states in the near threshold regions. The present results are compared with experimental ones given by Bizau et al and earlier theoretical ones. Excellent agreement is obtained between our theoretical results and the experimental photoionization cross sections. The present calculations show a significant improvement over the previous theoretical results.
Recently, direct measurements of fission cross-sections for 233Pa (n, f) reaction are available which stimulated the calculation of fission cross-sections for this reaction. For this calculation we have derived an analytical barrier formula based on microscopic-macroscopic description by fitting the actinide fission barrier data for the double humped barrier. Pairing effects have also been taken into account. The cross sections calculated for using the analytical barrier formula with the code EMPIRE 2.19 give better agreement with the available measurements. (author)
We are engaged in a multi-year project to study neutron scattering interactions in iron, the principal objective of which is to investigate the well-known deficiency that exists in reactor pressure vessel neutron fluence determinations. Specifically, we are using the spherical-shell transmission method, employing iron shells with different thicknesses, and neutron time-of-flight measurements of the scattered neutrons, in an effort to precisely determine specific energy regions over which deficiencies in the non-elastic scattering cross section for neutron scattering in iron appear to exist. The analysis of the experimental data involves correlating the data with theoretical calculations of neutron transport through the iron spheres in order to evaluate the degree to which the calculated neutron spectra predict the measured spectra relative to different types of particle interactions. In doing so, we have developed new methodologies for performing neutron transport calculations that will be useful to a range of transport problems. Preliminary results show good agreement between the experimental data and the calculated distribution of neutron flight times over much of the data range, except for the contribution due to breakup neutrons. (author)
Calculated cross sections in the reactions of (p, γ) radiative capture on 1p-shell target nuclei
A theoretical study of radiative capture reactions of protons on nuclei allow to obtain both truly nuclear information about structure of nuclei, energy spectra and a nuclear fusion, an elements occurrence and so on. Besides, the study of these reactions is necessary for diagnostics of thermonuclear plasma and a search of new alternative kinds of fuel for controlled thermonuclear fusion. However during the extraction of astrophysical data from the reactions there are observed the difficulties, which are connected with existence of wide resonance in the total cross section of the reactions give a direct capture. Within the framework of the method of distorted waves there were made calculations of differential cross sections of the reaction of radiative capture for E1, E2, and M1 transitions. To describe the input channel there was used a phenomenological optical potential. This potential was obtained from analysis of experimental data of elastic scattering of proton by nuclei. Fixing geometrical parameters depth of potential was varied. Then energy dependence of parameters was deduced. These approach for extraction of potential parameters from experimental data were applied for protons interaction with 9Be, 14N and 12C nuclei. Another approach for obtaining of an interaction potential of proton with the nucleus is a cluster-folding potential. In this approach a nuclear target was considered as the cluster system (thus an internal structure of clusters did not considered) and folding procedure was conducted by cluster-cluster interaction and cluster density. Cluster-folding potential was used for interaction of protons with 9Be and 16O nuclei. Potentials obtained in these both approach were applied for calculation of radiative capture reaction 9Be(p, γ)10B, 11B(p, γ)12C, 12,13C(p, γ)13,14N, 14N(p, γ)15O, 16O(p, γ)17F. Results of calculation are compared with data of other works and experimental data. Comparison of our results with results of other works shows
1 - Description of program or function: specified on ORNL-RSIC-25, shielding benchmark problems. - BP-3 (Neutron cross sections): Format: ANISN, DOT and MORSE; Number of groups: 22 neutron / 18 gamma-ray; Nuclides: air; Origin: ENDF/B; Weighting spectrum: 1/E; - BP-6 (neutron and gamma-ray cross sections): Format: ANISN, DOT and MORSE; Number of groups: 22 neutron / 18 gamma-ray; Nuclides: Borated Polyethylene (C-12, H, and B-10); Origin: ENDF/B-II. The cross section data can be used to repeat the Shielding Benchmark Problems 3.0 and 6.0 for testing against the results published in ORNL-RSIC-25. 2 - Method of solution: ZZ-BP-3 neutron cross sections from the CCC-17/05R library were processed into 104 neutron groups using the PSR-9/CSP code. The fine-group neutron cross sections were collapsed to 22 broad groups using CCC-254/ANISN with an equilibrium fission spectrum source. The resulting multigroup cross sections are P5 coefficients punched on cards in format suitable for input to ANISN, DOT, and MORSE. ZZ-BP-6 neutron and gamma-ray cross sections for 12C, H, and 10B were from ENDF/B-II data. The neutron multigroup cross sections were generated into 104 neutron groups using the PSR-13/SUPERTOG code. The fine-group neutron cross sections were collapsed to 22 broad groups using CCC-254/ANISN with an equilibrium fission spectrum source. The gamma-ray multigroup cross sections were generated using PSR-7/MUG. The neutron-gamma-ray coupling utilized yield data from the DLC-12/POPOP4 library (data sets 010101, 060101, 060301, and 05100201). The neutron-gamma-ray coupled multigroup cross-section set was generated using the SAMPLE COUPLING CODE (ASCC). The multigroup cross sections are in a 22-18 group structure with P3 coefficients punched on cards in format suitable for input to ANISN, DOT, and MORSE
Motivated by a need for an economical yet rigorous tool which can address the computation of the structural material Doppler effect, an extremely efficient improved RABANL capability has been developed utilizing the fact that the Doppler broadened line shape functions become essentially identical to the natural line shape functions or Lorentzian limits beyond about 100 Doppler widths from the resonance energy, or when the natural width exceeds about 200 Doppler widths. The computational efficiency has been further enhanced by preprocessing or screening a significant number of selected resonances during library preparation into composition and temperature independent smooth background cross sections. The resonances which are suitable for such pre-processing are those which are either very broad or those which are very weak. The former contribute very little to the Doppler effect and their self-shielding effect can readily be averaged into slowly varying background cross section data, while the latter contribute very little to either the Doppler or to self-shielding effects. To illustrate the accuracy and efficiency of the improved RABANL algorithms and resonance screening techniques, calculations have been performed for two systems, the first with a composition typical of the STF converter region and the second typical of an LMFBR core composition. Excellent agreement has been found for RABANL compared to the reference Monte Carlo solution obtained using the code VIM, and improved results have also been obtained for the narrow resonance approximation in the ultra-fine-group option of MC2-2
There are several new technological application fields of fast neutrons such as accelerator-driven incineration/ transmutation of the long-lived radioactive nuclear wastes (in particular transuranium nuclides) to short-lived or stable isotopes by secondary spallation neutrons produced by high-intensity, intermediate-energy, charged-particle beams, prolonged planetary space missions, shielding for particle accelerators. Especially, accelerator driven subcritical systems (ADS) can be used for fission energy production and /or nuclear waste transmutation as well as in the intermediate-energy accelerator driven neutron sources, ions and neutrons with energies beyond 20 MeV, the upper limit of exiting data files that produced for fusion and fission applications. In these systems, the neutron scattering cross sections and emission differential data are very important for reactor neutronics calculations. The transition rate calculation involves the introduction of the parameter of mean free path determines the mean free path of the nucleon in the nuclear matter. This parameter allows an increase in mean free path, with simulation of effect, which is not considered in the calculations, such as conservation of parity and angular momentum in intra nuclear transitions. In this study, we have investigated the multiple preequilibrium matrix element constant from internal transition for Uranium, Thorium, (n,xn) neutron emission spectra. The neutron-emission spectra produced by (n,xn) reactions on nuclei of some target (for spallation) have been calculated. In the calculations, we have used the geometry dependent hybrid model and the cascade exciton model including the effects of the preequilibrium. The pre-equilibrium direct effects have been examined by using full exciton model. All calculated results have been compared with the experimental data. The obtained results have been discussed and compared with the available experimental data and found agreement with each other
Díez, C. J.; Cabellos, O.; Martínez, J. S.
2015-01-01
Several approaches have been developed in last decades to tackle nuclear data uncertainty propagation problems of burn-up calculations. One approach proposed was the Hybrid Method, where uncertainties in nuclear data are propagated only on the depletion part of a burn-up problem. Because only depletion is addressed, only one-group cross sections are necessary, and hence, their collapsed one-group uncertainties. This approach has been applied successfully in several advanced reactor systems like EFIT (ADS-like reactor) or ESFR (Sodium fast reactor) to assess uncertainties on the isotopic composition. However, a comparison with using multi-group energy structures was not carried out, and has to be performed in order to analyse the limitations of using one-group uncertainties.
A computational method for calculating multigroup self-shielded cross sections in heterogeneous media containing arbitrary mixtures of resonant isotopes is presented. The method accounts for resonance interference between immixed resonant nuclei as well as for spatial resonance interference between resonant isotopes in different geometrical locations. A general correction is used to generate an intermediary reaction-rate library for resonant isotopic mixtures from a single-isotope, standard preprocessed library. Reaction rates for the heterogeneous fine-structure equation are computed from the intermediary library by invoking an equivalence theorem either on a group basis or using Bell's factors defined on macrogroups. Results are presented for a homogeneous mixture of Uranium oxide as well as for a recycled-fuel PWR cell. A study of the radial dependence of self-shielding for a recycled mixture of Uranium-Plutonium oxide in a PWR cell and in a submoderated cell is also included
Calculation of the photoionization with de-excitation cross sections of He and helium-like ions
The results of the calculation of the photoionization with de-excitation of excited He and helium-like ions Li+ and B3+ at high but nonrelativistic photon energies ω are discussed. Several lower 1S and 3S states are considered. The ratios Rd+* of the cross sections of photoionization with de-excitation, σ(d)+*(ω), and of the photoionization with excitation, σ+*(ω) are presented and analyzed. The dependence of Rd+* on the excitation of the target object and the charge of its nucleus is presented. In addition to theoretical interest, the results obtained can be verified using long-lived excited states such as 23S of He
We suggest a procedure for estimating uncertainties in neutron cross sections calculated with a nuclear model descriptive of a specific mass region. It applies standard error propagation techniques, using a model-parameter covariance matrix. Generally, available codes do not generate covariance information in conjunction with their fitting algorithms. Therefore, we resort to estimating a relative covariance matrix a posteriori from a statistical examination of the scatter of elemental parameter values about the regional representation. We numerically demonstrate our method by considering an optical-statistical model analysis of a body of total and elastic scattering data for the light fission-fragment mass region. In this example, strong uncertainty correlations emerge and they conspire to reduce estimated errors to some 50% of those obtained from a naive uncorrelated summation in quadrature. 37 references
Śpiewanowski, M D; Horbatsch, M; Kirchner, T
2016-01-01
Inner-shell vacancy production for the O$^{8+}$-Li collision system at 1.5 MeV/amu is studied theoretically. The theory combines single-electron amplitudes for each electron in the system to extract multielectron information about the collision process. Doubly-differential cross sections obtained in this way are then compared with the recent experimental data by LaForge et al. [J. Phys. B 46, 031001 (2013)] yielding good resemblance, especially for low outgoing electron energy. A careful analysis of the processes that contribute to inner-shell vacancy production shows that the improvement of the results as compared to single-active-electron calculations can be attributed to the leading role of two-electron excitation-ionization processes.
Description is given for the Photon programme written for the Ibm 370/168 computer in Fortran 4. language. The programme calculates the photoreaction cross-sections, polarization and asymmetries for closed shell nuclei in RPA theory
Aydinol, M.; Aydeniz, D.
2016-03-01
L shell ionization cross section and Li subshells ionization cross sections of Os, Pt, Hg, Pb, Po atoms calculated. For each atom, ten different electron impacty energy values Eoi used. Calculations carried out by using nonrelativistic Lotz equation in Matlab. Ionization cross section values obtained for Eoi values in the energy range of ELi ≤Eoi≤4ELi for each atom. Starting allmost from Eoi = ELi (i = 1,2,3) values of the each subshell ionization threshold energy, ionization cross section are increasing rapidly with Eoi. For a fixed Eoi = 3. ELi values, while Z increases from Z = 76 to Z = 84, ionization cross section are decrease. These results help to understand some results which obtained from other electron-sigle atom impact studies on σLi subshells.
The Fortran IV code PAPIN has been developed to calculate cross section probability tables, Bondarenko self-shielding factors and average self-indication ratios for non-fissile isotopes, below the inelastic threshold, on the basis of the ENDF/B prescriptions for the unresolved resonance region. Monte-Carlo methods are utilized to generate ladders of resonance parameters in the unresolved resonance region, from average resonance parameters and their appropriate distribution functions. The neutron cross-sections are calculated by the single level Breit-Wigner (SLBW) formalism, with s, p and d-wave contributions. The cross section probability tables are constructed by sampling the Doppler-broadened cross sections. The various self-shielded factors are computed numerically as Lebesgue integrals over the cross section probability tables. The program PAPIN has been validated through extensive comparisons with several deterministic codes
Munoz-Cobos, J. G.
1981-08-01
A FORTRAN 4 code was developed to calculate cross section probability tables, Bondarenko self-shielding factors, and average self-indication ratios for non-fissile isotopes, below the inelastic threshold, on the basis of prescriptions for the unresolved resonance region. Monte-Carlo methods are utilized to generate ladders of resonance parameters in he unresolved resonance region, from average resonance parameters and their appropriate distribution functions. The neutron cross sections are calculated by the single level Breit-Wigner formalism, with s, p and d-wave contributions. The cross section probability tables are constructed by sampling the Doppler-broadened cross sections. The various self-shielded factors are computed numerically as Lebesgue integrals over the cross section probability tables. The program was validated through extensive comparisons with several deterministic codes.
The program for calculation of the cross sections of neutron interaction with deformed nuclei by the strongly coupled channel method in the adiabatic approximation is described. The results of test calculations of cross sections of elastic and inelastic neutron scattering with initial energy of 0.1; 0.6; 2.0; 2.5 MeV on the sup(238)U nucleus are presented
Kaganovich, Igor D.; Startsev, Edward A.; Davidson, Ronald C.
2003-01-01
Stripping cross sections in nitrogen have been calculated using the classical trajectory approximation and the Born approximation of quantum mechanics for the outer shell electrons of 3.2GeV I$^{-}$ and Cs$^{+}$ ions. A large difference in cross section, up to a factor of six, calculated in quantum mechanics and classical mechanics, has been obtained. Because at such high velocities the Born approximation is well validated, the classical trajectory approach fails to correctly predict the stri...
U. Schneider
2009-01-01
Full Text Available The paper presents the structural application of a new thermal induced strain model for concrete – the TIS-Model. An advanced transient concrete model (ATCM is applied with the material model of the TIS-Model. The non-linear model comprises thermal strain, elastic strain, plastic strain and transient temperature strains, and load history modelling of restraint concrete structures subjected to fire.The calculations by finite element analysis (FEA were done using the SAFIR structural code. The FEA software was basically new with respect to the material modelling derived to use the new TIS-Model (as a transient model considers thermal induced strain. The equations of the ATCM consider a lot of capabilities, especially for considering irreversible effects of temperature on some material properties. By considering the load history during heating up, increasing load bearing capacity may be obtained due to higher stiffness of the concrete. With this model, it is possible to apply the thermal-physical behaviour of material laws for calculation of structures under extreme temperature conditions.A tunnel cross section designed and built by the cut and cover method is calculated with a tunnel fire curve. The results are compared with the results of a calculation with the model of the Eurocode 2 (EC2-Model. The effect of load history in highly loaded structures under fire load will be investigated.A comparison of this model with the ordinary calculation system of Eurocode 2 (EC2 shows that a better evaluation of the safety level was achieved with the new model. This opens a space for optimizing concrete structure design with transient temperature conditions up to 1000 °C.
Evaluation of ion-atom charge-changing cross-sections is needed for many accelerator applications. A Classical Trajectory Monte Carlo (CTMC) simulation has been used to calculate ionization and charge-exchange cross-sections. For benchmarking purposes, an extensive study has been performed for the simple case of hydrogen and helium targets in collisions with various ions. Despite the fact that the simulation only accounts for classical mechanics, the calculations are comparable to experimental results for projectile velocities in the region corresponding to the vicinity of the maximum cross-section. The shortcomings of the CTMC method for multielectron target atoms are discussed.
Kaganovich, I D; Davidson, R C; Kaganovich, Igor D.; Startsev, Edward A.; Davidson, Ronald C.
2003-01-01
Stripping cross sections in nitrogen have been calculated using the classical trajectory approximation and the Born approximation of quantum mechanics for the outer shell electrons of 3.2GeV I$^{-}$ and Cs$^{+}$ ions. A large difference in cross section, up to a factor of six, calculated in quantum mechanics and classical mechanics, has been obtained. Because at such high velocities the Born approximation is well validated, the classical trajectory approach fails to correctly predict the stripping cross sections at high energies for electron orbitals with low ionization potential.
Calculation of the neutron induced fission cross-section of 233Pa up to 20 MeV
Since very recently, direct measurements of the 233Pa(n,f) cross-section are available in the energy range from 1.0 to 8.5 MeV. This has stimulated a new, self-consistent, neutron cross-section evaluation for the n+233Pa system, in the incident neutron energy range 0.01-20 MeV. Since higher fission chances are involved also the lighter Pa-isotopes had to be re-evaluated in a consistent manner. The results are quite different compared to earlier evaluation attempts. Since 233Pa is a key isotope in the thorium based fuel cycle the quality of its reaction cross-sections is important for the modeling of future advanced fuel and reactor concepts. The present status of the evaluated libraries is that they differ by a factor of two in the absolute fission cross-section and also in the threshold energy value
ZZ DLC-2D/100G, 100 Neutron-Group Cross-Section Library by SUPERTOG Calculation for ANISN, DOT
1 - Nature of physical problem solved: Format: ANISN, DOT or DTF-4; Number of groups: 100; Nuclides: H, D, He, He-3, Li-6, Li-7, Be-9, B-10, B-11, C-12, N-14, O-16, Na-23, Mg, Al-27, Si, Cl, K, Ca, V, Cr, Mn-55, Fe, Co-59, Ni, Cu, Cu-63, Cu-65, Nb, Mo, Ag-107, Xe-135, Cs-133, Sm-149, Eu-151, Eu-153, Gd, Dy-164, Lu-175, Lu-176, Ta-181, Ta-182, W-182, W-183, W-184, W-186, Re-185, Re-187, Au-197, Pb, Th-232, Pa-233, U-234, U-235, U-238, Pu-238, Pu-239, Pu-240, Pu-241, Pu-242, Am-241, Am-243, and Cm-244. Origin: The nuclides in DLC-2 are those which have been released as category I ENDF/B by the National Neutron Cross Section Center, Brookhaven National Laboratory. Weighting spectrum: The explicit assumption was made that the flux has the shape of a fission spectrum joined at 0.0674 MeV by a 1/E tail. Neutron transport calculations can be performed with DLC-2 data. Since the data are intended for use in multigroup discrete-ordinates or Monte Carlo transport codes which treat anisotropic scattering, possible cross section angular expansion is limited only by the options available in the particular code used. Specifically, the retrieval program manipulates DLC-2 such that it conforms to input requirements of the ANISN, DOT, or DTF-4 codes, or any computer code using data in the ANISN or DTF-4 format. The nuclides in DLC-2 are those which have been released as category I ENDF/B by the National Neutron Cross Section Center, Brookhaven National Laboratory. The library contains data for H, D, He, 3-He, 6-Li, 7-Li, 9-Be, 10-B, 11-B, 12-C, 14-N, 16-O, 23-Na, Mg, 27-Al, Si, Cl, K, Ca, V, Cr, 55-Mn, Fe, 59-Co, Ni, Cu, 63-Cu, 65-Cu, Nb, Mo, 107-Ag, 135-Xe, 133-Cs, 149-Sm, 151-Eu, 153-Eu, Gd, 164-Dy, 175-Lu, 176-Lu, 181-Ta, 182-Ta, 182-W, 183-W, 184-W, 186-W, 185-Re, 187-Re, 197-Au, Pb, 232-Th, 233-Pa, 234-U, 235-U, 238-U, 238-Pu, 239-Pu, 240-Pu, 241-Pu, 242-Pu, 241-Am, 243-Am, and 244-Cm. 2 - Method of solution: DLC-2 was generated by SUPERTOG from nuclear data in either point
R. Vogt
2007-01-01
We assess the theoretical uncertainties on the total charm cross section. We discuss the importance of the quark mass, the scale choice and the parton densities on the estimate of the uncertainty. We conclude that due to the small charm quark mass, which amplifies the effect of the other parameters in the calculation, the uncertainty on the total charm cross section is difficult to quantify.
Goriely, S; Krewald, S
2011-01-01
The E1 strength function for 15 stable and unstable Sn even-even isotopes from A=100 till A=176 are calculated using the self-consistent microscopic theory which, in addition to the standard (Q)RPA approach, takes into account the single-particle continuum and the phonon coupling. Our analysis shows two distinct regions for which the integral characteristics of both the giant and pygmy resonances behave rather differently. For neutron-rich nuclei, starting from $^{132}$Sn, we obtain a giant E1 resonance which significantly deviates from the widely-used systematics extrapolated from experimental data in the $\\beta$-stability valley. We show that the inclusion of the phonon coupling is necessary for a proper description of the low-energy pygmy resonances and the corresponding transition densities for $A132$ region the influence of phonon coupling is significantly smaller. The radiative neutron capture cross sections leading to the stable $^{124}$Sn and unstable $^{132}$Sn and $^{150}$Sn nuclei are calculated wi...
Calculations of cross sections of neutron induced reactions for 52Cr in 6-20 MeV energy range have been performed using Hauser-Feshbach code developed by the author. The calculations include cross sections of (n,n'), (n.np), (n,2n), (n,p), (n,pn), (n,pγ), (n,α), (n,αγ) and (n, αn) reactions induced in 52Cr. The calculations have been compared with measurements and evaluations. (author). 30 refs, 11 figs, 2 tabs