Measurements of the Neutron-Induced Fission Cross Sections of ²⁴⁰Pu, ²⁴²Pu, and ²⁴⁴Pu Relative to ²³⁵U from 0.1 to 30 MeV

We have measured the fission cross-section ratios ²⁴⁰Pu:²³⁵U, ²⁴²Pu:²³⁵U, and ²⁴⁴Pu:²³⁵U as a function of neutron energy from 0.1 to 30 MeV using ionization fission chambers, the time-of-flight technique, and the threshold method at the Lawrence Livermore Laboratory 100-MeV electron linear accelerator. The measured cross-section ratios, averaged over the neutron energy interval from 1.75 to 4.00 MeV, are 1.366 ± 0.025, 1.110 ± 0.019, and 0.979 ± 0.020, respectively.