A Capture-gated Fast Neutron Detection Method

TL;DR

This paper introduces a cadmium-based capture-gated fast neutron detector that addresses 3He shortages, achieving notable detection efficiency and dual neutron-gamma measurement capabilities for radiation portal monitors.

Contribution

The paper presents a novel cadmium-based detector design that improves neutron detection efficiency and enables simultaneous neutron and gamma-ray detection, replacing traditional 3He detectors.

Findings

Detection efficiency of 21.66% achieved.

Low false alarm rates for neutron and gamma sources.

Effective for radiation portal monitoring applications.

Abstract

To address the problem of the shortage of neutron detectors used in radiation portal monitors (RPMs), caused by the 3He supply crisis, research on a cadmium-based capture-gated fast neutron detector is presented in this paper. The detector is composed of many 1 cm * 1 cm * 20 cm plastic scintillator cuboids covered by 0.1 mm thick film of cadmium. The detector uses cadmium to absorb thermal neutrons and produce capture gamma-rays to indicate the detection of neutrons, and uses plastic scintillator to moderate neutrons and register gamma-rays. This design removes the volume competing relationship in traditional 3He counter-based fast neutron detectors, which hinders enhancement of the neutron detection efficiency. Detection efficiency of 21.66 +- 1.22% has been achieved with a 40.4 cm * 40.4 cm * 20 cm overall detector volume. This detector can measure both neutrons and gamma-rays simultaneously. A small detector (20.2 cm * 20.2 cm * 20 cm) demonstrated a 3.3 % false alarm rate for a 252Cf source with a neutron yield of 1841 n/s from 50 cm away within 15 seconds measurement time. It also demonstrated a very low (< 0.06%) false alarm rate for a 3.21 * 105 Bq 137Cs source. This detector offers a potential single-detector replacement for both neutron and the gamma-ray detectors in RPM systems.