Speaker
Description
This research involves investigations into the pulse shape discrimination (PSD) capacity of a fast neutron and gamma-ray plastic scintillator, EJ-276, and the characterisation of waveforms created as a result of interactions of both particle types. Whereas most scintillators can only be used for the detection of gamma-rays, the EJ-276 is a robust plastic scintillator designed for detection and identification of fast neutrons in mixed radiation fields, such as those the in environment surrounding a nuclear reactor. The PSD capacity of the detector stems from the different characteristic waveform decay times for fast neutrons and gamma-rays, based off the different nuclear reactions which occur in the scintillation volume of the detector. The material of which the scintillator is made from retains the key advantages of using plastic scintillators, such as its robustness, fast-timing response and scalability to large detector volumes while retaining its PSD capacity.
Alongside the EJ-276 detector research a validated Monte-Carlo simulation of the experimental facility in which all experimental measurements have been taken has been developed. The thermal neutron rate detected using 3He gas-filled detectors, as a function of both polythene moderator thickness and borated polythene shield thickness was used to characterise the experimental facility. The moderator and shields were arranged in different configurations to gain a full understanding of the neutron spectrum in the whole environment. As well as experimental relationships between moderator thickness and the thermal neutron count rate the simulation was also validated using neutron and gamma dose rate measurements, which were found to be in agreement at the 95% confidence level.
The performance of existing detectors will be presented, such as the direct measurements of neutron flux using 3He gas-filled detector; utilising their outputs to develop a fully validated Monte-Carlo model of the experimental neutron laboratory. Research completed using the EJ-276 plastic scintillator will also be presented with topics such as gamma-ray pulse shape characterisation, pulse amplification and multiple PSD methods. The overall aim of this research is to produce a robust, compact, cost-effective solution for measuring two types of radiation simultaneously in a mixed radiation field such as the area surrounding a nuclear reactor with the minimum equipment requirements to maintain adequate PSD.