Large-scale Gadolinium-doped Water Cerenkov Detector for Non-Proliferation

TL;DR

This paper presents the design, construction, and simulation of a large-scale gadolinium-doped water Cerenkov detector for detecting correlated neutrons and gamma-rays from nuclear fission, aiding non-proliferation efforts.

Contribution

It introduces a novel large-scale water Cerenkov detector with detailed response modeling for neutron and gamma detection in non-proliferation applications.

Findings

Neutron detection efficiency varies with position within the detector.

The detector's energy response has been characterized through simulation.

Simulation results provide insights into detector performance for fission event detection.

Abstract

Fission events from Special Nuclear Material (SNM), such as highly enriched uranium or plutonium, can produce simultaneous emission of multiple neutrons and high energy gamma-rays. The observation of time correlations between any of these particles is a significant indicator of the presence of fissionable material. Cosmogenic processes can also mimic these types of correlated signals. However, if the background is sufficiently low and fully characterized, significant changes in the correlated event rate in the presence of a target of interest constitutes a robust signature of the presence of SNM. Since fission emissions are isotropic, adequate sensitivity to these multiplicities requires a high efficiency detector with a large solid angle with respect to the target. Water Cerenkov detectors are a cost-effective choice when large solid angle coverage is required. In order to characterize the neutron detection performance of large-scale water Cerenkov detectors, we have designed and built a 3.5 kL water Cerenkov-based gamma-ray and neutron detector, and modeled the detector response in Geant4 [1]. We report the position-dependent neutron detection efficiency and energy response of the detector, as well as the basic characteristics of the simulation.