Improved FIFRELIN de-excitation model for neutrino applications

TL;DR

This paper enhances the FIFRELIN de-excitation model by incorporating experimental data, angular correlations, and improved electron and X-ray treatments, to better simulate Gd isotope de-excitation for neutrino detection experiments.

Contribution

The paper introduces new features in FIFRELIN, including experimental transition data, gamma-ray angular correlations, and refined electron and X-ray modeling, improving its accuracy for neutrino-related applications.

Findings

Enhanced de-excitation modeling accuracy.

Improved simulation of neutron capture in Gd isotopes.

Repository of updated FIFRELIN simulations available.

Abstract

The precise modeling of the de-excitation of Gd isotopes is of great interest for experimental studies of neutrinos using Gd-loaded organic liquid scintillators. The FIFRELIN code was recently used within the purposes of the STEREO experiment for the modeling of the Gd de-excitation after neutron capture in order to achieve a good control of the detection efficiency. In this work, we report on the recent additions in the FIFRELIN de-excitation model with the purpose of enhancing further the de-excitation description. Experimental transition intensities from EGAF database are now included in the FIFRELIN cascades, in order to improve the description of the higher energy part of the spectrum. Furthermore, the angular correlations between {\gamma} rays are now implemented in FIFRELIN, to account for the relative anisotropies between them. In addition, conversion electrons are now treated more precisely in the whole spectrum range, while the subsequent emission of X rays is also accounted for. The impact of the aforementioned improvements in FIFRELIN is tested by simulating neutron captures in various positions inside the STEREO detector. A repository of up-to-date FIFRELIN simulations of the Gd isotopes is made available for the community, with the possibility of expanding for other isotopes which can be suitable for different applications.