PHOTONEUTRON CROSS SECTIONS IN SILICON AND CALCIUM

1953 ◽  
Vol 31 (1) ◽  
pp. 70-77 ◽  
Author(s):  
R. G. Summers-Gill ◽  
R. N. H. Haslam ◽  
L. Katz
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Neutron Yield ◽  
Threshold Energy ◽  
Threshold Effect ◽  
Monitoring Method ◽  
Dose Monitoring ◽  
Γ Rays ◽  
Integrated Cross Section ◽  
Peak Value

Using the dropping apparatus and dose monitoring method previously reported, the cross sections for the reactions Si28(γ, n)Si27 and Ca40(γ, n)Ca39 have been measured by detecting positron activities in the residual nuclei. The Si28(γ, n)Si27 cross section has a peak value of 21 mbarns at 20.9 Mev. and an integrated cross section to 24 Mev. of 0.070 Mev-barns. The threshold energy is 16.9 ± 0.1 Mev. The Ca40(γ, n)Ca39 cross section has a peak value of 15 mbarns at 19.3 Mev. and an integrated cross section to 24 Mev. of 0.065 Mev-barns. The threshold is 15.8 ± 0.1 Mev.A comparison of our results with the neutron yield measurement of Price and Kerst at 18 and 22 Mev. gives good agreement. A further comparison with the neutron yield work of Baldwin and Elder is made.The sharp discontinuity in (γ, n) yields using lithium γ rays observed by Wäffler and Hirzel is explained as a threshold effect. Integrated cross sections increase more or less smoothly with Z.In addition, improved values for the half-lives of the residual nuclei Si27 and Ca39 have been measured. These are 4.45 ± 0.05 and 1.00 ± 0.03 sec. respectively.

PHOTONEUTRON THRESHOLD AND CROSS SECTION FOR 71Lu175

1958 ◽  
Vol 36 (4) ◽  
pp. 415-418 ◽  
Author(s):  
H. J. King ◽  
L. Katz
Keyword(s):  
Cross Section ◽  
Neutron Yield ◽  
Giant Resonance ◽  
Threshold Energy ◽  
Half Width ◽  
Bremsstrahlung Energy ◽  
Resonance Cross Section ◽  
Integrated Cross Section ◽  
Peak Value

The neutron yield resulting from photoneutron reactions in Lu175 has been measured as a function of peak bremsstrahlung energy up to 23 Mev. The threshold energy for this reaction was found to be 7.77 ± 0.05 Mev. The giant resonance cross section has a peak value of 225 millibarns at 16 Mev., a half-width of 8.4 Mev., and an integrated cross section to 23 Mev. of 1.9 Mev-barns.

THE MEASUREMENT OF PHOTONUCLEAR CROSS SECTIONS IN ISOTOPES LEADING TO SHORT-LIVED DECAY PRODUCTS

1952 ◽  
Vol 30 (3) ◽  
pp. 257-269 ◽  
Author(s):  
R. N. H. Haslam ◽  
R. G. Summers-Gill ◽  
E. H. Crosby
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Half Life ◽  
Half Width ◽  
Reaction Threshold ◽  
Parent Materials ◽  
Dosage Rate ◽  
Decay Products ◽  
Integrated Cross Section ◽  
Peak Value

A dropping apparatus, including a new means of dosage rate monitoring, has been designed to allow the observation of short-lived activities produced by betatron irradiation of various parent materials. The photonuclear cross section for the reaction S32(γ, n)S31 has been measured by this means. The cross section has a peak value of 24.6 millibarns at 20.1 ± 0.5 Mev., a half width of 4.5 Mev., and an integrated cross section of 0.12 Mev-barns. The reaction threshold was found to be 15.0 ± 0.1 Mev. The experiment has also yielded a new half life for S31 − 2.66 ± 0.03 sec.

THE (γ, n) AND (γ, p) CROSS SECTIONS OF ARGON40

1954 ◽  
Vol 32 (9) ◽  
pp. 593-598 ◽  
Author(s):  
D. McPherson ◽  
E. Pederson ◽  
L. Katz
Keyword(s):  
Cross Section ◽  
Photon Energy ◽  
Cross Sections ◽  
Integrated Cross Section ◽  
Peak Value

The (γ, n) and (γ, p) cross sections in A40 have been measured as a function of photon energy from threshold to 24 Mev. The (γ, n) cross section was found to have a peak value of 38 mbarns at 20 Mev. and an integrated cross section of 0.35 Mev-barn. These values for the (γ, p) cross section were found to be 120 mbarns at > 25 Mev. and 0.54 Mev-barn respectively. In spite of the higher (γ, p) threshold, it was found that the two cross sections were equal at 19.5 Mev. and above this energy the (γ, p) cross section became larger. This interesting result is discussed.

Evaluation of Optical Model Potential Using Neutron Induced Cross Section Reaction for Spherical Uranium-238 Isotope up to 20MeV

2015 ◽  
Vol 59 ◽  
pp. 26-34
Author(s):  
Iman Tarik Al-Alawy ◽  
Ronak Ikram Ali
Keyword(s):  
Experimental Data ◽  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Optical Model ◽  
Threshold Energy ◽  
Model Potential ◽  
Model Parameters ◽  
Incident Neutron ◽  
Optical Model Potential

The evaluation are based on mainly on the calculations of the nuclear optical model potential and relevant parameters are collected and selected from References Input Parameter Library (RIPL) which is being developed under the international project coordinated by the International Atomic Energy Agency (IAEA). The analyzing of a complete energy range has done starting from threshold energy for each reaction. The cross sections are reproduced in fine steps of incident neutron energy with 0.01MeV intervals with their corresponding errors. The recommended cross sections for available experimental data taken from EXFOR library have been calculated for all the considered neutron induced reactions for U-238 isotopes. The calculated results are analyzed and compared with the experimental data. The optimized optical potential model parameters give a very good agreement with the experimental data over the energy range 0.001-20MeV for neutron induced cross section reactions (n,f), (n,tot), (n,el), (n,inl), (n,2n), (n,3n), and (n,γ) for spherical U-238 target elements.

Photoneutron Cross Sections in 14N

1972 ◽  
Vol 50 (15) ◽  
pp. 1689-1696 ◽  
Author(s):  
R. W. Gellie ◽  
K. H. Lokan ◽  
N. K. Sherman ◽  
R. G. Johnson ◽  
J. I. Lodge
Keyword(s):  
Excited States ◽  
Cross Section ◽  
Cross Sections ◽  
Neutron Emission ◽  
Giant Resonance ◽  
Sequential Decay ◽  
Dipole Resonance ◽  
Intermediate States ◽  
Integrated Cross Section ◽  
High Degree

Photoneutron distributions from 14N have been obtained by time-of-flight methods, for bremsstrahlung end-point energies increasing in 2 MeV steps from 15.5 to 29.5 MeV. A large part of the neutron yield is associated with the sequential decay of 14N to 12C, through well-defined intermediate states of 13C, at 7.55, 8.86, and 11.80 MeV, which are unstable against neutron emission. The (γ,n0) cross section for neutron emission to the ground state of 13N is found to agree very closely with the corresponding (γ,p0) cross section, implying a high degree of isospin purity for the giant dipole resonance of 14N. It is observed that the decay of the giant resonance proceeds freely through those odd-parity excited states of the A = 13 nuclei which are single hole states formed by the removal of a p-shell nucleon from the parent 14N.The integrated cross section for all neutron-producing interactions is found to be 88 ± 5 MeV mb.

scholarly journals Direct and Dissociative Ionization Cross Section of Oxygen Molecule from Threshold to 10 KeV

2019 ◽  
Vol 8 (6S3) ◽  
pp. 1365-1368
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Ionization Cross Section ◽  
Threshold Energy ◽  
Theoretical Data ◽  
Oxygen Molecule ◽  
Dissociative Ionization ◽  
Ionization Cross ◽  
Section Data ◽  
Ionization Cross Sections

Due to abundant applications of ionization in various fields of applied sciences, it’s desirable to calculate absolute ionization cross sections of various atoms or molecules. In this literature, we have calculated the absolute direct and dissociative ionization cross sections of the oxygen molecule from threshold energy to 10,000 eV by using revisited Jain-Khare semi-empirical approach. In this literature, the total direct and absolute ionization cross section data have compared with easily available experimental and/or theoretical data. The present results give a better account for the ionization cross sections up to higher incident electron energies.

scholarly journals Optical Model Potential Using CINDA Library for Neutron Induced Cross Section Reactions for Spherical Uranium-235,238 Isotopes

2015 ◽  
Vol 60 ◽  
pp. 66-73
Author(s):  
Iman Tarik Al-Alawy ◽  
Ronak Ikram Ali
Keyword(s):  
Experimental Data ◽  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Optical Model ◽  
Threshold Energy ◽  
Model Potential ◽  
Model Parameters ◽  
Incident Neutron ◽  
Optical Model Potential

The calculation are based mainly on the nuclear optical model potential and relevant parameters are collected and selected from References Input Parameter Library (RIPL) which is being developed under the international project coordinated by the International Atomic Energy Agency (IAEA). The analyzing of a complete energy range has done starting from threshold energy for each reaction. The cross sections are reproduced in fine steps of incident neutron energy with 0.01MeV intervals with their corresponding errors. The recommended cross sections for available experimental data taken from CINDA library have been calculated for all the considered neutron induced reactions for spherical U-235 and U-238 isotopes. The calculated results are analyzed and compared with the experimental data. The optimized optical potential model parameters give a very good agreement with the experimental data over the energy range 0.001-20MeV for neutron induced cross section reactions (n,f), (n,tot), (n,el), (n,inl), (n,2n), (n,3n), and (n,γ) for spherical U-235 and U-238 target elements.

scholarly journals Scattering of slow neutrons

1937 ◽  
Vol 162 (908) ◽  
pp. 127-143 ◽  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Ionization Chamber ◽  
Percentage Increase ◽  
Quantitative Interpretation ◽  
Total Cross Sections ◽  
Paraffin Block ◽  
Γ Rays ◽  
Absorbing Elements ◽  
Slow Neutrons

The adsorption and scattering of slow neutrons have been studied by various methods. In their first survey, Amaldi, D'Agostino, Fermi, Pontecorvo, Rasetti and Segré (1935) investigated the absorption of slow neutrons by different elements inside a paraffin block. The number of slow neutrons capture in an indicator (e. g. silver). The values for the absorption coefficients which they obtained with this arrangement can be regarded as a measure of the ''true'' absorption of slow neutrons. Later, Dunning, Pegram, Fink and Mitchell (1935) measured the "total" cross-sections, i. e. the sum of the well-defined beam of slow neutrons, and a lithium-coated ionization chamber as indicator. Recently, Griffiths and Szilard (1937) have determined the cross-section of some strongly absorbing elements using the captured γ-rays from cadmium as indicator. The scattering of slow neutrons was studied for some elements by MItchell and Murphy (1935), Mitchell, Murphy and Whitaker (1936), Budnitzky and Kurtschatow (1935) Pontecorvo and Wick (1936), and others. In these experiments, the slow neutrons issuing from a paraffin block passed through an indicator (e. g. silver), and were scattered backwards from the substance under investigation. When thin scattered are used, the percentage increase of the radioactivity produced in the indicator gives a measure of the scattering cross-section. This method has the disadvantage, even in the case of good scatters, that the increase in the radioactivity of the indicator is usually small compared with the effect due to the primary neutrons. A quantitative interpretation of the results may be further complicated by the fact that the neutrons leave the surface of the paraffin block at angles from 0 to 90°. Also, multiple scattering is not avoided.

The coherent scattering of γ -rays by K electrons in heavy atoms - II. The scattering of 0·32 mc 2 γ -rays in mercury

1954 ◽  
Vol 227 (1168) ◽  
pp. 59-72 ◽  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absorptive Part ◽  
Coherent Scattering ◽  
Heavy Atoms ◽  
University Of Cambridge ◽  
Γ Rays ◽  
The Cross ◽  
The University ◽  
Scattering Cross Sections

The results of calculations for the coherent scattering of γ -rays of energy 0·32 mc 2 by K electrons in mercury are given in a form which enables one to determine scattering cross-sections at any angle, for any initial and final polarizations and for any spin orientation of the electrons. The method used in doing the computation is that described in part І, the main part of the work having been performed on the EDSAC computer at the University of Cambridge. The dispersive contribution to the cross-section agrees with previous approximate calculations. The absorptive part is calculated as well and has the effect of adding to the cross-section a contribution approximately equal to one-sixth of the dispersive contribution at all angles of scattering.

Transmission Electron Diffraction at 200 eV and Damage Thresholds below the Carbon K Edge

2000 ◽  
Vol 6 (4) ◽  
pp. 368-379
Author(s):  
Michael R. Stevens ◽  
Qing Chen ◽  
Uwe Weierstall ◽  
John C.H. Spence
Keyword(s):  
Electron Diffraction ◽  
Cross Section ◽  
Single Molecule ◽  
Cross Sections ◽  
Threshold Energy ◽  
Low Energy ◽  
Transmission Electron Diffraction ◽  
Transmission Electron ◽  
Minimum Number ◽  
Shell Ionization

Abstract Transmission electron diffraction patterns from ultra-thin aromatic and aliphatic organic films at beam energies of 200 eV–1 keV have been recorded in a custom low energy electron transmission (LEET) chamber. A significant reduction of the molecular damage cross-section, measured by fading of diffraction spots, was found for thin films of the aromatic perylene when the beam energy was reduced from 400 to 200 eV. The corresponding measurements for the aliphatic tetracontane showed a smaller “threshold energy” and the differences are discussed. Electron beam damage from other aromatic materials has also been studied at low energy. Comparison of the carbon K shell ionization cross-section and the measured damage cross-sections show that carbon K-shell ionization is strongly correlated with the damage observed in aromatics at beam energies higher than 284 eV. Calculation of the minimum number of unit cells needed for imaging a single molecule, and comparison of calculated elastic with measured damage cross-sections both indicate new possibilities for imaging biomolecules with low energy electrons.

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