Study of Stability and Consistency of EAS Thermal Neutron Detection at ENDA-64

TL;DR

This study evaluates the stability and consistency of thermal neutron detection by the ENDA-64 array at LHAASO, analyzing environmental influences and calibration results to ensure reliable measurements for cosmic ray research.

Contribution

It provides a comprehensive analysis of the stability and environmental effects on neutron detection in the ENDA-64 array, enhancing data reliability for cosmic ray studies.

Findings

Calibration shows up to 6.85% inconsistency across clusters.

Event and neutron rate stability within 4.68% and 11%.

Sand cubes improve neutron collection and protect detectors.

Abstract

Introduction:Electron-Neutron Detector Array (ENDA) is designed to measure thermal neutrons produced by hadronic interactions between cosmic ray extensive air showers (EAS) and the surrounding environment as well as electrons around the cores of EAS. ENDA is located within Large High Altitude Air Shower Observatory (LHAASO). ENDA was expanded from an initial 16 detectors to 64 detectors in April 2023, so called ENDA-64, and has been running alongside LHAASO. The stability and consistency of neutron detection are crucial for laying a solid foundation for subsequent data analysis and physical results. Methods:We obtain the stability by studying variations of event rate and thermal neutron rate in each cluster and the consistency by comparing distribution of number of thermal neutrons between clusters. Additionally, we investigate the specific influences of the rainy and dry seasons, as well as the presence or absence of sand cubes under the detectors, to examine the environmental factors affecting neutron measurement performance. Results:The calibration results indicate good consistency in thermal neutron detection across the clusters, with the maximum inconsistency of 6.85%. The maximum instability of event rate and thermal neutron rate over time are 4.68% and 11.0% respectively. The maximum inconsistency between the clusters without the sand cubes is 18%. The use of sand cubes is effective in protecting the target material from rainwater, and the sand cubes help the cluster to increase collection of neutrons generated by EAS events.