Sensitivity of Measured Fission Yields on Prompt-neutron Corrections

Abstract

Although the number of emitted prompt neutrons from the fission fragments increases as a function of excitation energy, it is not fully understood whether the increase in ν¯ (A) as a function of En is mass dependent. The share of excitation energies among the fragments is still under debate, but there are reasons to believe that the excess in neutron emission originates only from the heavy fragments, leaving ν¯light (A) almost unchanged. We have investigated the consequences of a mass-dependent increase in ν¯ (A) on the final mass and energy distributions. The analysis have been performed on experimentally measured data on 234U (n, f). The assumptions concerning ν¯ (A) are essential when analysing measurements based on the 2E-technique, and impact significantly on the measured observables. For example, the post-neutron emission mass yield distribution revealed changes up to 10–30 %. The outcome of this work pinpoints the urgent need to determine ν¯ (A) experimentally, and in particular, how ν¯ (A) changes as a function of incident neutron energy. Many fission yields in the data libraries could be largely affected, since their analysis is based on a different assumption concerning the neutron emission.