Little Boy neutron spectrum below 3 MeV
The leakage neutron spectrum from the Little Boy replica has been measured from 12 keV to 3 MeV using a high-resolution /sup 3/He ionization chamber, and from 1 keV to 3 MeV using proton-recoil proportional counters. The /sup 3/He-spectrometer measurements were made at distances of 0.75 and 2.0 m from the active center and at angles of 0/sup 0/, 45/sup 0/, and 90/sup 0/ with respect to the axis of the assembly. Proton-recoil measurments were made at 90/sup 0/ to the assembly axis at distances of 0.75 and 2.0 m, with a shielded measurement made at 2.0 m to estimate background due to scattering. The /sup 3/He spectrometer was calibrated at Los Alamos using monoenergetic /sup 7/Li(p,n)/sup 7/Be neutrons to generate a family of response functions. The proton-recoil counters were calibrated at Argonne by studying the capture of thermal neutrons by nitrogen in the counters, by observation of the 24-keV neutron resonance in iron, and by relating to the known hydrogen content of the counters. The neutron spectrum from Little Boy was found to be highly structured, with peaks corresponding to minima in the iron total neutron cross section. In particular, influence of the 24-keV iron window was evident in both sets of spectra. The measurements provide information for dosimetry calculations and also a valuable intercomparison of neutron spectrometry using the two different detector types. Spectra measured with both detectors are in essential agreement. 8 references, 7 figures, 2 tables.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Argonne National Laboratory (ANL), Argonne, IL (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 6809066
- Report Number(s):
- LA-UR-84-1523; CONF-840627-3; ON: DE84012631
- Resource Relation:
- Conference: 29. annual meeting of the Health Physics Society, New Orleans, LA, USA, 3 Jun 1984; Other Information: Portions are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS
NUCLEAR WEAPONS
NEUTRON SPECTRA
EXPERIMENTAL DATA
HIROSHIMA
NEUTRON LEAKAGE
ASIA
DATA
INFORMATION
JAPAN
NUMERICAL DATA
SPECTRA
WEAPONS
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