Little Boy neutron spectrum below 1 MeV

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A high-resolution /sup 3/He ionization chamber of the type development by Cuttler and Shalev was used to study the neutron spectrum from the Little Boy mockup. Measurements were made at distances of 0.75 and 2.0 m and at angles of 0/sup 0/, 45/sup 0/, and 90/sup 0/ with respect to the axis of the assembly, which was operated at power levels from 8.6 to 450 mW. Detector efficiency as a function of energy as well as parameters for correction of pulse-height distributions for proton-recoil and wall effects were determined from a set of response functions for monoenergetic neutrons measured at ... continued below

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Pages: 9

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Evans, A.E. January 1, 1984.

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Description

A high-resolution /sup 3/He ionization chamber of the type development by Cuttler and Shalev was used to study the neutron spectrum from the Little Boy mockup. Measurements were made at distances of 0.75 and 2.0 m and at angles of 0/sup 0/, 45/sup 0/, and 90/sup 0/ with respect to the axis of the assembly, which was operated at power levels from 8.6 to 450 mW. Detector efficiency as a function of energy as well as parameters for correction of pulse-height distributions for proton-recoil and wall effects were determined from a set of response functions for monoenergetic neutrons measured at the Los Alamos 3.75-MeV Van de Graaff Accelerator Facility. Pulse-shape discrimination was used to separate /sup 3/He-recoil pulses from the pulse-height distribution. The spectrum was found to be highly structured, with peaks corresponding to minima in the total neutron cross section of iron. In particular, 15% of the neutrons above the epithermal peak in energy were found to be in the 24-keV iron window. Lesser peaks out to 700 keV are also attributable to filtering action of the weapon's heavy iron casing. Data taken using experimental proton-recoil proportional counters are compared with the high-resolution spectra.

Physical Description

Pages: 9

Notes

NTIS, PC A02/MF A01.

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  • 17. midyear topical meeting of the Health Physics Society, Pasco, WA, USA, 5 Feb 1984

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  • Other: DE84003794
  • Report No.: LA-UR-83-3329
  • Report No.: CONF-840202-6
  • Grant Number: W-7405-ENG-36
  • Office of Scientific & Technical Information Report Number: 5506165
  • Archival Resource Key: ark:/67531/metadc1088451

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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Creation Date

  • January 1, 1984

Added to The UNT Digital Library

  • Feb. 10, 2018, 10:06 p.m.

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  • May 23, 2018, 12:26 p.m.

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Evans, A.E. Little Boy neutron spectrum below 1 MeV, article, January 1, 1984; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc1088451/: accessed April 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.