Parameters of the best approximation of reduced neutron widths distribution. Actinides

TL;DR

This paper analyzes the parameters of the best approximation for reduced neutron widths distribution in actinides, using data from the ENDF/B-VII library, and discusses the variability and estimation of these parameters.

Contribution

It introduces a method to approximate neutron widths distributions with variable partial items and studies the determination of their parameters from experimental data.

Findings

Mean neutron amplitudes can significantly differ from zero.

Dispersions of widths can differ from mean widths.

Quantitative analysis requires comparison of models with estimated parameter dispersion.

Abstract

The data of ENDF/B-VII library on reduced neutron widths for nuclei 231Pa, 232Th, 233,234,235,236,238U, 237Np, 239,240,241,242Pu, 241,243Am and 243Cm (including p-resonances of 232Th, 238U, 239Pu) in form of cumulative sums in function on Gamma0n/<Gamma0n> were approximated by variable number K of partial items 0<K<5. Parameters of approximation -- mean value of neutron amplitude, its dispersion and portion of contribution of part of widths of distribution number K in their total sum. The problems of their determination from distributions of different number of squares of normally distributed random values with variable threshold of loss of some part of the lowest widths values were studied. It was obtained for some part of neutron resonances that their mean amplitudes can considerably differ from zero value, and dispersions - from mean widths. And it is worth while to perform any quantitative analysis of widths distributions by means of comparison of different model notions with obligatory estimation of random dispersion of the desired parameters.