Post-neutron mass yield distribution and photo-neutron cross-section measurements in Bi-209 with 65-MeV Bremsstrahlung

Abstract

The post-neutron-emission mass yield distribution and the photo-neutron cross-section (sigma (gamma,3n)) of Bi-209 with 65-MeV bremsstrahlung have been determined using an off-line gamma-ray spectrometric technique in the test electron linac at Pohang Accelerator Laboratory. The post-neutron mass yield distribution in 65-MeV bremsstrahlung induced fission of Bi-209 is symmetric with average mass around 103 and a FWHM of 22 mass units, which is higher than the literature value of 19 mass units in the energy range of 28 - 40 MeV. The increasing trend of the FWHM of the post-neutron mass yield distribution with increasing breamsstrahlung energy has been explained from the point of view of the increase in the multi-chance fission probabilities with increasing excitation energy. The (gamma,3n) reaction cross-section is determined for the first time. It was also calculated using the TALYS code and was found to be in good agreement with the experimental value.