Investigation of the prompt neutron emission mechanism in low energy fission of^235,233U(n_th, f) and²⁵²Cf(sf)

Abstract

Abstract.A series of experiments has been performed to measure prompt neutron angular and energy distributions from thermal neutron-induced fission of 235,233 U in correlation with the fission fragments. These distributions have been analyzed with the assumption of neutron isotropic emission from accelerated fission fragments. The performed analysis demonstrates that all obtained results can be described within 5% accuracy using this assumption. This discrepancy is approximately constant and doesn't depend on fragment mass and the total kinetic energy (TKE). Some minor peculiarities of angular distribution may be interpreted as a result of anisotropy of the fission neutron angular distribution in the fragment center-of-mass system.

Prompt neutron emission and energy balance in 235U(n,f)

“…8, results in −∂TKE/∂ν = 11.86 MeV/n. This value is substantially lower than the values 16.7-18.5 MeV/n determined in earlier studies, performed at thermal incident neutron energies [23][24][25][26]. This inverse slope is closely related to the energy cost to emit a neutron (although it should not be directly interpreted as this quantity [19]).…”

“…Distribution of the fragment TKE obtained in this study compared to data of Refs. [23][24][25]. The dotted black line is the result obtained by folding the present data set with a gaussian resolution function with σ = 8.2 MeV, necessary to reproduce the data of Nishio et al The vertical dashed line labeled Q max indicates the maximum available energy as determined by the fragmentation where the heavy fragment is the doubly magic 132 Sn nucleus [27].…”

“…Dependence of prompt neutron multiplicity per fission on the fragment TKE obtained in this study, compared to data from Refs. [23][24][25][26]. The data of Ref.…”

“…The average neutron multiplicity per fragment as a function of the fragment mass from this study compared to data from Refs. [23,24] and the evaluation by Wahl [18].…”

“…The data of Ref. [24] has been re-binned for better clarity of the figure. The full black line is a linear least squared fit to the data from this study, which corresponds to an inverse slope of −∂TKE/∂ν = 11.86 MeV/n.…”