Simultaneous Measurement of Fission Fragments and Prompt Neutrons for Thermal Neutron-induced Fission of U-235

摘要

Simultaneous measurement of fission fragments and prompt neutrons following the thermal neutron induced fission of U-235 has been performed in order to obtain the neutron multiplicity (ν) and its emission energy (η) against the specified mass (m~*) and the total kinetic energy (TKE). The obtained value of - dv/dTKE(m~ *) showed a saw-tooth distribution. The average neutron energy <η>(m *) had a distribution with a reflection symmetry around the half mass division. The measurement also gave the level density parameters of the specified fragment, a(m~*), and this parameters showed a saw-tooth trend too. The analysis by a phenomenological description of this parameters including the shell and collective effects suggested the existence of a collective motion of the fission fragments.