THE PROBABILITY RATIO OF THE TERNARY FISSION OF URANIUM-235 AND URANIUM-238 BY NEUTRONS OF VARIOUS ENERGIES

The dependence of the ternary fission probability on the excitation energy of the fissioning nucleus must be determined in order to clarify the mechanism of the process; tests were therefore carried out, using CsI(Tl) crystals for detecting the long-range alpha particles from the /sup 235/U and / sup 238/U targets under a body angle of 2 pi . Neutrons from the D(d,n)/sup 3/He and T(d,n)/sup 4/He reactions, with energies of 2.5 and 14 Mev, respectively, were used for the irradiation. The ternary fission events were identified by the alpha particle-fission fragment coincidence. The following probability ratios were obtained for the ternary fission: for /sup 235/U W/sub E/sub n/ = 2.5 Mev/W/ sub slow/ = 0.95 plus or minus 0.08; W/sub E/sub n/ = 14 Mev/W/sub slow/ = 1.21 plus or minus 0.17. The data indicated that within the limits of the experimental error, the probability of the ternary fission does not change in the case of fission by slow, 2.5, and 14-Mev neutrons. For the dependence of the ternary fission on the excitation energy, the values reported by R. Nobles (Phys. Rev., 126: 1508(1962)) were also taken into consideration; it was concluded that the probability of the ternary fission remainsmore » unchanged in the various binary fission channels. (TTT)« less