Nuclear fission and reaction study at the JAEAE tandem facility

西尾 勝久   

Nishio, Katsuhisa

I will present recent results on nuclear fission and multinucleon transfer reactions obtained at the JAEA tandem facility. Earlier studies of spontaneous fission of heavy actinides found that the fission fragments mass distribution suddenly changes from predominantly asymmetric to symmetric, when the mass number of the fissioning nucleus becomes larger than 257. We have measured for the first time fission-fragment mass and total-kinetic-energy (TKE) distributions of the excited compound nucleus Md* (Z=101), populated in the reaction He + Es, using the rare radioactive target isotope Es. The fission of Md can be interpreted as involving 3 fission modes: one mass-asymmetric and two mass-symmetric fission modes, the latter two are manifested by different TKE values. In this assumption, symmetric and asymmetric fission modes have nearly similar yields at the excitation energy of 15.0 MeV. The spectrum of 18.0 MeV can be explained as due to the increase of asymmetric fission mode. The results are demonstrated using 6-dimensional Langevin calculation.