Point-by-Point model description of experimental average prompt neutron multiplicity as a function of total kinetic energy of fission fragments

Abstract

The present Point by Point (PbP) model calculations of average prompt neutron multiplicity as a function of total kinetic energy 〈ν〉(TKE), performed for three fissioning systems 252Cf(SF), 239Pu(nth, f) and 235U(nth, f), describe very well the experimental data over the entire TKE range, including not only the slope dTKE/dν but also the flattening of experimental 〈ν〉 data at low TKE values.Present deterministic PbP model results of 〈ν〉(TKE) are analyzed comparatively with previous PbP 〈ν〉(TKE) results based on the same multi-parametric matrix ν(Z, A, TKE) and different manners of averaging this matrix over the fission fragment distributions, as well as with previous and recent results of probabilistic Monte Carlo treatments.The average model parameters as a function of TKE provided by the PbP treatment exhibit nice and regular behaviours and can be fitted well. The resulted model parameter dependences on TKE allow the use of the most probable fragmentation approach (Los Alamos model with subsequent improvements) having the advantages to provide results at many TKE values in a very short calculation time (compared to the PbP model and Monte Carlo treatments) and also outside the TKE range where the PbP model is applicable.Possible explanations of discrepancies between the slopes of different sets of experimental 〈ν〉(TKE) data are mentioned, too.