Measurement of Fission Neutron Multiplicities for Thorium-232 and Uranium-235 with Incident Neutron Energies to 49 MeV

Neutron Multiplicity in the Fission ofU238andU235with Neutrons up to 200 MeV

“…In particular, it is interesting to investigate in which proportions the heated system releases the excess energy with prefission neutron and light charged particle (LCP) emission on the one hand, and increase of excitation energy and angular momentum of the primary fragments on the other hand. Prompt-fission-neutron multiplicities (the average of which is denoted by p ) for neutron-induced fission of uranium were measured by Fréhaut [9] in the 1970s from 1.5 to 28 MeV for 235 U and 238 U. Howe et al [10] completed the measurement up to 49 MeV for 235 Un; f in the 1980s. But beside points on 238 Up; f at energies below 60 MeV [11], only one measurement was reported at intermediate energies at 156 MeV [12].…”

“…The second method utilized in this work consists of detecting the neutrons with smaller liquid scintillators at a distance from a target sensitive to fission fragments. A double time-of-flight technique is used to determine the incident neutron energy and the emitted neutron energy to build the fission neutron spectrum (FNS) as a function of the incident neutron energy [10]. A quantity proportional to p is simply obtained from the ratio of the integration of the FNS to the number of fission events.…”

“…The vertical error bars represent the systematic errors from the normalization; the horizontal ones represent the experimental resolution of the energies of the incident neutrons. Existing sparse data points [10,12] at intermediate energies are also presented for comparison. The neutron detectors in the case of Cheifetz et al [12] were at 90 to the beam.…”

“…Prompt-fission neutron average multiplicity for the system 235 Un; f as a function of incident neutron energy (open circles).Our data are not corrected for the undetected neutrons but are normalized to the data from[9] (black dots). Data from[10] are plotted with a .…”

Measurement of the Average Multiplicity of Prompt-Fission Neutrons from 238U(n,f) and 235U(n,f) from 0.7 to 200 MeV

“…Howe et al . [12] completed the measurement up to 49 MeV for 235U(n,f) in the 1980's . But beside points on 238U(p, f) at energies below 60 MeV [14], only one measurement was reported at intermediate energies at 156 MeV [13] .…”