Elastic and inelastic neutron scattering cross sections for natPb, 209Bi and natta in the energy range from 2 MeV to 4 MeV

The N-15(p,n) neutron source recently installed at the PTB cyclotron facility was used to measure neutron scattering cross sections at selected energies between 2 MeV and 4 MeV using lead, bismuth, and tantalum samples of natural isotopic composition. Angular distributions for elastic neutron scattering as well as for inelastic scattering involving the low-lying levels of Ta-181, (206,207)Pbi, Bi-209 were determined. Differential cross sections were derived using a full Monte Carlo simulation of the experiment and an iterative adaptation scheme for the differential cross sections to correct for the effect of multiple interactions in the samples and partial overlap of time-of-flight peaks corresponding to adjacent levels. The integrated cross sections agree well with earlier measurements carried out in Studsvik/Sweden. They show, however, significant deviations from recent data for level cross sections derived from measurement from the photoemission cross section.