Long-term evolution of the neutron rate at the Canfranc Underground Laboratory

TL;DR

This study presents the first long-term, energy-sensitive measurement of neutron rates at an underground lab, analyzing environmental influences over 412 days to support low-background experiments.

Contribution

It provides the first extensive, energy-resolved neutron rate data over time in an underground environment, including environmental correlations.

Findings

Neutron rate varies over time and energy levels.

Environmental factors influence neutron background.

Long-term data enhances background modeling for experiments.

Abstract

We report results on the long-term variation of the neutron counting rate at the Canfranc Underground Laboratory, of importance for several low-background experiments installed there, including rare-event searches. The measurement campaign was performed employing the High Efficiency Neutron Spectrometry Array (HENSA) mounted in Hall A and lasted 412 live days. The present study is the first long-term measurement of the neutron rate with sensitivity over a wide range of neutron energies (from thermal up to 0.1 GeV and beyond) performed in any underground laboratory so far. Data on the environmental variables inside the experimental hall (radon concentration, air temperature, air pressure and humidity) were also acquired during all the measurement campaign. We have investigated for the first time the evolution of the neutron rate for different energies of the neutrons and its correlation with the ambient variables.