Measurement of fission neutron multiplicities for thorium-232 and uranium-235 with incident neutron energies to 49 MeV
Fission neutron multiplicities have been measured for neutrons incident on /sup 232/Th with energies ranging from 1.1 to 49 MeV and for neutrons incident on /sup 235/U with energies from 17 to 49 MeV. The Lawrence Livermore National Laboratory 100-MeV electron Linac was used to produce a white source of neutrons. Incident neutron energies were measured using time-of-flight techniques. Fission neutrons were detected in a liquid scintillator using pulse-shape discrimination. All /sup 232/Th neutron multiplicities were measured relative to /sup 235/U at each incident neutron energy. Above 15 MeV the multiplicities were determined for /sup 232/Th and /sup 235/U by using lower energy data from the /sup 235/U sample to measure the neutron detector efficiency. Corrections for angular anisotropy and spectral temperatures of the fission neutrons were minimized through the use of a spherical shell of /sup 235/U surrounding the fission chamber. The present results for /sup 232/Th extend available multiplicity data into the previously unreported regions: 1.1 to 1.3 MeV and 17 to 49 MeV. The /sup 235/U results also extend significantly beyond previously reported data. For the /sup 232/Th case, previously observed deviations from linearity below 2 MeV and near the (n, n'f) threshold have been confirmed. In addition, this experiment suggests a continued rise in neutron multiplicity with decreasing incident neutron energy down to 1.1 MeV. A value for /sup -/v /SUB p/ of /sup 231/Th(n,f) is inferred from the /sup 232/Th results above the (n, n'f) threshold. The /sup 232/Th measurements reported here for neutron energies above 15 MeV show an average value of dE /SUB n/ /d/sup -/v /SUB p/, which agrees with a value calculated from the binding energies of the pre-scission evaporated neutrons and the assumed mean kinetic energies. The /sup 235/U data do not exhibit such a close agreement.
- Research Organization:
- University of California, Lawrence Livermore National Laboratory Livermore, California
- OSTI ID:
- 6581073
- Journal Information:
- Nucl. Sci. Eng.; (United States), Vol. 86:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
FISSION NEUTRONS
MULTIPLICITY
NEUTRON REACTIONS
FAST FISSION
THORIUM 232 TARGET
URANIUM 235 TARGET
ANISOTROPY
BINDING ENERGY
ENERGY DEPENDENCE
EXCITATION
EXPERIMENTAL DATA
LINEAR ACCELERATORS
LIQUID SCINTILLATORS
MEV RANGE 01-10
MEV RANGE 10-100
NEUTRON SOURCES
NEUTRON SPECTRA
NUCLEAR STRUCTURE
PULSE DISCRIMINATORS
THORIUM 231
TIME-OF-FLIGHT SPECTROMETERS
ACCELERATORS
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
BARYON REACTIONS
BARYONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
DATA
DISCRIMINATORS
ELECTRONIC CIRCUITS
ELEMENTARY PARTICLES
ENERGY
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EVEN-ODD NUCLEI
FERMIONS
FISSION
HADRON REACTIONS
HADRONS
HEAVY NUCLEI
HOURS LIVING RADIOISOTOPES
INFORMATION
ISOTOPES
MEASURING INSTRUMENTS
MEV RANGE
NEUTRONS
NUCLEAR REACTIONS
NUCLEI
NUCLEON REACTIONS
NUCLEONS
NUMERICAL DATA
PARTICLE SOURCES
PHOSPHORS
PULSE CIRCUITS
RADIATION SOURCES
RADIOISOTOPES
SPECTRA
SPECTROMETERS
TARGETS
THORIUM ISOTOPES
652026* - Nuclear Properties & Reactions
A=220 & above
Experimental- Spontaneous & Induced Fission- (-1987)