抄録
Distributions of fragment kinetic energies and masses in the 55 MeV proton-induced fission of U238 have been measured in various directions with respect to the beam by using a back-to-back arrangement of surface-barrier detectors. The observed energy distribution showed a single broad peak with a slight shoulder on the high energy side. This indicates a marked growth of symmetric fission. The most probable value of the total fragment kinetic energy was observed to be 156±5 MeV. The initial total kinetic energy before neutron emission was estimated from the value to be about 161 MeV. The mass distribution obtained in the transverse direction was in fair agreement with the radiochemical result. By making a fine comparison between these results, an attempt was made to obtain some information about neutron yields from individual fragments. The mass distribution in the backward direction was almost the same in shape as in the transverse direction, when corrected for the projectile momentum. Furthermore, the observed angular distribution of the composite fragments was less anisotropic than expected from the Halpern-Strutinski theory.
