High resolution measurement of neutron inelastic scattering and (n,2n) cross-sections for Bi-209

摘要

Gamma production cross-sections were measured for the neutron inelastic scattering and (n, 2n gamma) reactions on Bi-209 using the white neutron spectrum of GELINA with the time-of-flight technique at the 200 m flight-path station. The full energy range, from the inelastic threshold up to 20 MeV was covered in one experiment with an unprecedented energy resolution of 1.1 keV at 1 MeV and 35 keV at 10 MeV. The gamma-rays were detected with large volume HPGe detectors. The flux was determined with a U-235 fission chamber based on the U-235(n, f) standard cross-section. A metallic Bi sample was used. Inelastic gamma production cross-sections were measured for 39 transitions up to an excitation energy of 3.8 MeV. Based on the adopted level scheme of Bi-209, the total inelastic and the level cross-sections were constructed. A total uncertainty smaller than 5% was obtained for the total inelastic cross-section up to 10 MeV. The (n, 2n) gamma production cross-section was measured for the 8 transitions from Bi-208 nucleus up to 1.09 MeV excitation energy. The results are compared with earlier experimental works and with model calculations performed with the TALYS code, version 0.72. Calculations with the TALYS model code show good agreement with the deduced total inelastic cross-section in the entire incident energy range and for deduced level cross-sections below 3 MeV. Discrepancies between calculation and experiment that occur for gamma production cross-sections above 3 MeV are discussed. (c) 2007 Elsevier B.V. All rights reserved.