Measurement of fission cross section with neutron slowing-down spectrometer

The lead slowing-down neutron spectrometer designed for measurements of fission cross sections is described. The spectrometer allows to perform measurements both with very small quantities of investigated nuclei and small cross sections using the high-current linear electron accelerator FAKEL as a pulsed source of neutrons. The fission cross section of 235 U is used for the data normalization. The plate avalanche counters are used to detect the fission fragments. The fission cross sections for 237 Np, 236,239,241 Pu, 241,242m Am, 245 Cm and 249 Cf in the energy range of 0.1 - 100 keV are presented. The neutron flux anisotropy and its negligibly small distortions while using small quantities if nuclei (from 1 up to 300 μg) assure the measurement simultaneously with several isotopes. Basing on the experimental data obtained and using the correction procedure for the resolution function, the mean fission cross sections are calculated in the set of intervals of the 26 groups constant system