Prescission neutron emission in {sup 235}U({ital n}{sub th},{ital f}) through fragment-neutron angular correlation studies
- Nuclear Physics Division, Bhabha Atomic Research Centre, Bombay 400 (India)
Measurements of prompt neutron energy spectra and angular distributions from mass and kinetic energy selected fission fragments were carried out in the thermal neutron fission of {sup 235}U. Neutron energy was determined by the time-of-flight technique and fission fragment energy and angle were measured using a back-to-back gridded ionization chamber. The measured angular distributions of neutrons emitted from fragment pairs of various mass and kinetic energy were compared with results of Monte Carlo calculations assuming neutron emission from fully accelerated fragments to determine the component of neutrons which may be emitted in the prescission stage. The calculations were carried out using as inputs the measured center-of-mass neutron energy spectra and multiplicites and assuming isotropic emission of neutrons in the center-of-mass frame of both the fission fragments, and a three source fitting of the angular distributions was done to deduce the component of prescission neutrons. The value of the prescission neutron multiplicity averaged over all fragment masses is found to be 0.25{plus_minus}0.05 (about 10% of the total neutron multiplicity). The present results have been discussed on the basis of the energy damping and time scale of the saddle to scission transition in the thermal neutron induced fission process.
- OSTI ID:
- 55152
- Journal Information:
- Physical Review, C, Journal Name: Physical Review, C Journal Issue: 6 Vol. 51; ISSN PRVCAN; ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- English
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