High Resolution Measurements of Neutron-Induced Fission Cross Sections for ²³³U, ²³⁵U, ²³⁹Pu and ²⁴¹Pu Below 30 keV

Neutron-induced fission cross sections of ²³³U, ²³⁵U, ²³⁹Pu, and ²⁴¹Pu have been measured up to 30 keV. These measurements were performed with samples cooled down to liquid nitrogen temperature and with a nominal resolution of 1 nsec/m, using the 60-MeV Saclay LINAC as a pulsed-neutron source. The agreement with previously published results is within 3% for ²³⁵ U in the energy range 60 eV to 10 keV, and 6% for ²³³U below 1220 eV. For ²³⁹Pu and for ²⁴¹ Pu in the energy ranges 0.7 to 7 keV and 10 to 20 keV, the agreement is also within 6%. Total errors are a function of target material and incident neutron energies and hence are estimated to lie between 3 and 7%. The existence of an intermediate structure is demonstrated in the fission cross section of ²³⁹Pu.