A new compact neutron/gamma ray scintillation detector

A Buffler,A C Comrie,F D Smit,H J Wörtche

doi:10.1142/s2010194516602283

Abstract

Progress towards the realization of a new compact neutron spectrometer is described. The detector is based on EJ299-33 plastic scintillator coupled to silicon photomultipliers, and a digital implementation of pulse shape discrimination is used to separate events associated with neutrons from those associated with gamma rays. The spectrometer will be suitable over the neutron energy range 1–100 MeV, illustrated in this work with measurements made using an AmBe radioisotopic source and quasi-monoenergetic neutron beams produced using a cyclotron.

Highlights

There is an ongoing need to develop compact neutron spectrometers, for deployment in aircraft and spacecraft, for minerals exploration, for personal and workplace dosimetry and in security, for the detection of special nuclear materials
We present measurements of the response of EJ299-33 scintillators to neutrons and gamma rays from an a GBq 241Am9Be (AmBe) source and from a cyclotron beam
Neutrons and gamma rays were provided via two methods: a 2 GBq 241Am9Be (AmBe) radioisotopic source and proton beams produced at the cyclotron facility of iThemba LABS, South Africa

Summary

Introduction

There is an ongoing need to develop compact neutron spectrometers, for deployment in aircraft and spacecraft, for minerals exploration, for personal and workplace dosimetry and in security, for the detection of special nuclear materials. For dosimetry in the upper atmosphere and in space, neutrons in the energy range 1–100 MeV need to be measured.[1] This is an Open Access article published by World Scientific Publishing Company. Organic scintillation detectors remain strong candidates for these applications because the light output of certain organic scintillators display both fast and slow decay-components, related to the specific energy loss of the recoiling charged particle by the Birks relation.[2] Pulse shape discrimination (PSD), established[3] in the 1950s and developed through the 1960s, allows the identification of different types of charged particles in these scintillator detectors by means of the characteristics of the scintillation decay Liquid organic scintillators such as EJ301 remain a popular choice when good-quality PSD is required. We illustrate the use of a small EJ299-33-based detector for spectrometry by unfolding measured pulse height spectra using a response matrix calculated via a GEANT4-based simulation

Experiments

Pulse Shape Discrimination

Measurements with the AmBe Source

Measurements with a 140 MeV Proton Beam

Findings

Discussion and Conclusion