Dependence of anisotropy of emitted neutrons on total kinetic energy of fragments

The authors measured the dependence of the mean number of fission neutrons on the total kinetic energy of the fragments in the thermal neutron-induced fission of 235U. The measurements were performed for two neutron ejection angles (0 deg. and 90 deg.). The total fragment energy was determined by two semi-detector counters, while the neutrons were recorded by a scintillation counter. The neutrons were separated from the gamma quanta by the time-of-flight method. The authors determined the angular anisotropy of neutron ejection as a function of the total kinetic energy of the fragments. The calculations were performed according to the model which postulates the boiling-off of neutrons from excited fragments. The results obtained are discussed with special reference to the question whether there can be an additional mechanism for the emission of fission neutrons. (author)