# Flux measurement of fast neutrons in the Gran Sasso underground laboratory

## TL;DR

This study measures the fast neutron energy spectrum between 5 and 15 MeV in the Gran Sasso underground laboratory using a Gd-doped liquid scintillator, improving energy resolution over previous measurements.

## Contribution

The paper introduces an improved method for measuring the neutron spectrum with better energy resolution compared to prior work.

## Key findings

- Neutron spectrum measured between 5 and 15 MeV.
- Enhanced energy resolution achieved.
- Results compared favorably with existing literature.

## Abstract

The neutron energy spectrum for energies between 5 and 15 MeV has been measured in the INFN Laboratori Nazionali del Gran Sasso in Italy, by using a $1.5~m^3$ stainless-steel tank filled with 1.2 ton Gd-doped liquid scintillator. A two-pulse signature, composed of a prompt and a delayed signal, due to proton recoils and gammas from neutron capture on Gd respectively, has been used for events selection. The neutron energy spectrum has been obtained from the detected proton-recoil spectrum, after unfolding the detector response, which had been simulated with GEANT4. Although this spectrum has been measured previously, the present work represents an improvement in the energy resolution with respect to previously published results. The results obtained with this technique are compared with other measurements existing in literature.