THE EFFECT OF FLUCTUATIONS IN THE WIDTHS ON NEUTRON REACTION CROSS SECTIONS

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The general Wigner-Eisenbud theory is used to develop a method of analysis for the cross sections of fissionable nuclei. The method is employed in gdving a reasonable description of the low energy cross sections in U/sup 235/. The single level fit for U/sup 235/ is known to be unreasonable. Manylevel expressions for the cross sections are derived--the only approximation to the general theory being the neglect of all but a small group of resonances. It is shown that regardless of the number or definition of the fission channels the many-level expressions require few level parameters: the E/sub lambda /, GAMMA ... continued below

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Pages: 25

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Dresner, L. June 1, 1957.

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The general Wigner-Eisenbud theory is used to develop a method of analysis for the cross sections of fissionable nuclei. The method is employed in gdving a reasonable description of the low energy cross sections in U/sup 235/. The single level fit for U/sup 235/ is known to be unreasonable. Manylevel expressions for the cross sections are derived--the only approximation to the general theory being the neglect of all but a small group of resonances. It is shown that regardless of the number or definition of the fission channels the many-level expressions require few level parameters: the E/sub lambda /, GAMMA / sub lambda n/, GAMMA /sub lambda gamma / and GAMMA /sub lambda F/ of the single level theory for each resonance and a few additional parameters pertinent to the interference between levels. The interference terms are described and shown to be important. The shape and size of the U/sup 235/ cross sections below 2 ev are fitied to within one per cent using (a) only one negative energy resonance of smaller size than in the single level fits (b) no additional levels to fit the shape other than the observed levels at positive energiess (c) three interference purameters whose size suggests that there are several fission channels In U/sup 235/. This fit is better and more reasonable than the previous fits of the U/sup 235/ data. (auth)

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Pages: 25

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  • Other Information: Orig. Receipt Date: 31-DEC-58

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  • Report No.: CF-57-6-2
  • Grant Number: W-7405-ENG-26
  • DOI: 10.2172/4339633 | External Link
  • Office of Scientific & Technical Information Report Number: 4339633
  • Archival Resource Key: ark:/67531/metadc1026990

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  • June 1, 1957

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  • Oct. 15, 2017, 10:09 p.m.

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  • Oct. 23, 2017, 3:27 p.m.

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Dresner, L. THE EFFECT OF FLUCTUATIONS IN THE WIDTHS ON NEUTRON REACTION CROSS SECTIONS, report, June 1, 1957; Oak Ridge, Tennessee. (digital.library.unt.edu/ark:/67531/metadc1026990/: accessed December 14, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.