Gadolinium Loaded Cherenkov Detectors for Neutron Monitoring in High Energy Air Showers

TL;DR

This paper investigates the use of gadolinium-loaded water Cherenkov detectors for high-energy neutron monitoring in cosmic ray air showers, demonstrating potential detection efficiencies and improved background discrimination through simulations.

Contribution

It introduces a novel approach of using gadolinium-loaded WCDs for high-energy neutron detection and evaluates their efficiency and timing response via GEANT4 simulations.

Findings

Detection efficiency of 4-15% for neutrons above 200 MeV.

Gadolinium loading enhances timing response and background discrimination.

Extended gamma ray flash detection improves neutron interaction identification.

Abstract

Monitoring of high energy cosmic ray neutrons is of particular interest for cosmic ray water Cherenkov detectors as intense bundles of delayed neutrons have been found to arrive after the initial passage of a high energy air shower. In this paper we explore the possibility of building large-area high-energy neutron monitors using gadolinium-loaded Water Cherenkov Detectors (WCDs). GEANT4 simulations of photon production in WCDs are used to estimate the maximum detection efficiency for a hypothetical system. Requiring a series of neutron induced gamma ray flashes distributed over an extended period of time (up to 20{\mu}s) was shown to be an effective way to discriminate high energy neutron interactions from other backgrounds. Results suggest that neutron detection efficiencies of 4-15% may be possible using a gadolinium-loaded detection system above 200 MeV. The magnitude of gadolinium loading was also shown to significantly modify the timing response of the simulated detector.