LOW ENERGY NEUTRON CROSS SECTION OF MANGANESE

1955 ◽  
Vol 33 (11) ◽  
pp. 622-634 ◽  
Author(s):  
R. Krotkov
Keyword(s):  
Cross Section ◽  
Resonance Energy ◽  
Neutron Cross Section ◽  
Coherent Scattering ◽  
High Energy ◽  
Positive Energy ◽  
Matrix Formalism ◽  
Perfect Agreement ◽  
R Matrix ◽  
Section Curve

The total neutron cross section of Mn55 has three (predominantly scattering) resonances in the energy range 300–2500 ev. In the present paper these resonances are examined in detail from the point of view of the R matrix formalism. It is found that quite good (but not perfect) agreement with the experimental cross section curve is obtained by assigning (in order of increasing resonance energy) spins (2, 3, 3) and neutron widths (23, 11, 395 ev.) to the resonances. The addition of a constant increment ΔR11 = 0.16 × 10−12 cm. representing the contribution of distant, positive energy, J = 3 resonances to the R matrix element for s-neutron scattering improves agreement with experiment on the high energy side of the highest energy resonance. The (n, γ) cross section at 0.025 ev. is fitted well by a constant radiation width of 0.5 ev. However, with no set of parameters was it possible to fit both the experimental total cross section curve, and the observed coherent scattering cross section at 0 ev., although the sign of the latter was accounted for correctly. The discrepancy is 2.0 barns (calculated) compared to 1.7 barns (observed).

Resonance Widths and Unitarity

1972 ◽  
Vol 50 (2) ◽  
pp. 84-92 ◽  
Author(s):  
C. T. Tindle
Keyword(s):  
Energy Dependence ◽  
Cross Section ◽  
Matrix Theory ◽  
Neutron Cross Section ◽  
Matrix Formalism ◽  
R Matrix ◽  
Level Width ◽  
S Matrix ◽  
The Difference ◽  
Energy Dependent

The low energy neutron cross section of 135Xe is analyzed using both the R-matrix theory of Wigner and Eisenbud and the S-matrix theory of Humblet and Rosenfeld. Particular attention is given to the role played by the total resonance level width for it is well known that the R-matrix widths are energy dependent but the S-matrix widths are not. This different energy dependence leads to different analytic forms for the cross section and the n + 135Xe reaction offers what may be the simplest and best physical example for comparing these two forms. To the accuracy of the present data the difference is not detectable. The different energy dependence of the resonance widths is shown to be related to unitarity. A general proof that the R-matrix formalism is always unitary is given. The difficulty of satisfying unitarity in the S-matrix formalism is discussed and it is shown for the n + 135Xe reactions that this can lead to physically unacceptable solutions. This "lack of unitarity" does not, however, lead to any difficulties in fitting the present experimental data.

R-matrix calculations of photoionization cross section of Ne-like tungsten

2015 ◽  
Vol 93 (11) ◽  
pp. 1221-1226 ◽  
Author(s):  
Indu Khatri ◽  
Arun Goyal ◽  
Sunny Aggarwal ◽  
A.K. Singh ◽  
Man Mohan
Keyword(s):  
Cross Section ◽  
Energy Levels ◽  
Resonance Energy ◽  
Photoionization Cross Section ◽  
Distorted Wave ◽  
Rydberg Series ◽  
Close Coupling ◽  
R Matrix ◽  
Coupling Approximation ◽  
Wave Methods

The photoionization cross section calculation for the ground state 1s22s22p6 1S (J = 0) of Ne-like W64+ has been performed in the close-coupling approximation using the Dirac–Coulomb R-matrix method. The resonance structures are analysed and described by finding the resonance energy positions of prominent Rydberg series 2s2p6(2S)np 1P0 for W LXV ion. To calculate fine structure energy levels, multi-configuration Dirac–Fock and relativistic distorted-wave methods have been employed. Wherever possible we have compared our work with the available data. The present results will be useful for diagnostics and modeling of plasma in ITER and other fusion devices.

scholarly journals ELASTIC BACKSCATTERED CROSS-SECTIONS OF 14N(P,P0)14N AT HIGH ANGLES

2020 ◽  
Vol 20 (3) ◽  
pp. 749-754
Author(s):  
MOHAMED ELTAYEB M. EISA ◽  
JOHAN ANDRE MARS ◽  
MUSTAFA J. ABUALREISH ◽  
MARWA L. WAREGH
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Ion Beam ◽  
Region Of Interest ◽  
Laboratory Frame ◽  
Matrix Formalism ◽  
Cross Section Data ◽  
R Matrix ◽  
Section Data ◽  
Elastic Backscattering

The importance and present needs of proton cross section data of nitrogen needed by the Ion Beam Analysis (IBA) community are briefly reviewed. Previous experimental data presently used for the theoretical determination of the proton cross-sections are discussed. The Azure code based on the R-matrix formalism was then used to evaluate the data and to determine the nitrogen cross section in the previous and presently desired angular domain and energy region of interest. The experimental elastic backscattering cross section data, as spectra, for back-scattering analysis determined at angles in the laboratory frame of reference, θi,lab, of 165o, 170o and 176o are presented.

scholarly journals Calculation of electron scattering cross-section using different theoretical methods

2020 ◽  
Vol 239 ◽  
pp. 08005
Author(s):  
Xiazhi Li ◽  
Jinhui Zhu ◽  
Yinghong Zuo ◽  
Ya Li
Keyword(s):  
Partial Wave ◽  
Cross Section ◽  
Matrix Theory ◽  
High Energy ◽  
Scattering Cross Section ◽  
Low Energy ◽  
Energy Electron ◽  
R Matrix ◽  
Scattering Cross ◽  
Wave Methods

Aiming at the simulation of the fine process of the electron transportation in gamma detectors, we calculate electron differential scattering cross-section (DCS) of several typical materials including Fe, ethylene and polyethylene. Based on two different calculation methods, which are partial wave methods based on Dirac equation and R-matrix theory, we find differences of the cross section at low energy region. The result indicates that both partial wave method and R-matrix theory associated with independent atom method (IAM) are not suitable for low energy electron impacting on strong coupled molecule, for example, electron-ethylene. For high energy electron interacting with atom and molecule, the result shows no critical difference because the kinetic energy of the incident electron is severely higher than the electron bound energy in molecule or the excitation energy of a certain atom.

Preparation and verification of mixed high-energy neutron cross-section library for ADS

2018 ◽  
Vol 29 (10) ◽  
Author(s):  
Ze-Long Zhao ◽  
Yong-Wei Yang ◽  
Hai-Yan Meng ◽  
Qing-Yu Gao ◽  
Yu-Cui Gao
Keyword(s):  
Cross Section ◽  
Neutron Cross Section ◽  
High Energy ◽  
High Energy Neutron ◽  
Energy Neutron

In situ irradiation effects studies in medium- and high-voltage TEM

1995 ◽  
Vol 53 ◽  
pp. 234-235
Author(s):  
Charles W. Allen
Keyword(s):  
Cross Section ◽  
Particle Flux ◽  
Threshold Value ◽  
High Energy ◽  
Irradiation Damage ◽  
Defect Complexes ◽  
Lattice Position ◽  
Electrons And Ions ◽  
The Masses

With respect to structural consequences within a material, energetic electrons, above a threshold value of energy characteristic of a particular material, produce vacancy-interstial pairs (Frenkel pairs) by displacement of individual atoms, as illustrated for several materials in Table 1. Ion projectiles produce cascades of Frenkel pairs. Such displacement cascades result from high energy primary knock-on atoms which produce many secondary defects. These defects rearrange to form a variety of defect complexes on the time scale of tens of picoseconds following the primary displacement. A convenient measure of the extent of irradiation damage, both for electrons and ions, is the number of displacements per atom (dpa). 1 dpa means, on average, each atom in the irradiated region of material has been displaced once from its original lattice position. Displacement rate (dpa/s) is proportional to particle flux (cm-2s-1), the proportionality factor being the “displacement cross-section” σD (cm2). The cross-section σD depends mainly on the masses of target and projectile and on the kinetic energy of the projectile particle.

Investigation of the total neutron cross section for natural hafnium on the filtred neutron beam with energy 59 keV

2011 ◽  
Vol 30 (0) ◽  
pp. 142-147
Author(s):  
О. О. Грицай ◽  
А. К. Гримало ◽  
В. В. Колотий ◽  
В. М. Венедиктов ◽  
С. П. Волковецький ◽  
...  
Keyword(s):  
Cross Section ◽  
Neutron Beam ◽  
Neutron Cross Section ◽  
Total Neutron ◽  
Total Neutron Cross Section

scholarly journals Total cross sections of eγ → $$ eX\overline{X} $$ processes with X = μ, γ, e via multiloop methods

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Roman N. Lee ◽  
Alexey A. Lyubyakin ◽  
Vyacheslav A. Stotsky
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Elliptic Integral ◽  
High Energy ◽  
Calculation Methods ◽  
Complete Elliptic Integral ◽  
Total Cross Sections ◽  
Multiloop Calculation ◽  
The Cross ◽  
Analytical Expressions

Abstract Using modern multiloop calculation methods, we derive the analytical expressions for the total cross sections of the processes e−γ →$$ {e}^{-}X\overline{X} $$ e − X X ¯ with X = μ, γ or e at arbitrary energies. For the first two processes our results are expressed via classical polylogarithms. The cross section of e−γ → e−e−e+ is represented as a one-fold integral of complete elliptic integral K and logarithms. Using our results, we calculate the threshold and high-energy asymptotics and compare them with available results.

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