High-energy Neutron-induced Fission Cross Sections of Natural Lead and Bismuth-209

The CERN Neutron Time-Of-Flight (n TOF) facility is well suited to measure small neutron- induced ssion cross sections, as those of subactinides. The cross section ratios of natPb and 209Bi relative to 235U and 238U were measured using PPAC detectors. The fragment coincidence method allows to unambiguously identify the ssion events. The present experiment provides the rst results for neutron-induced ssion up to 1 GeV for natPb and 209Bi. A good agreement with previous experimental data below 200 MeV is shown. The comparison with proton-induced ssion indicates that the limiting regime where neutron-induced and proton-induced ssion reach equal cross section is close to 1 GeV.