Comparison of Pulse Shape Discrimination Characteristics in Three Organic Scintillators for a High Resolution Coded-Aperture Neutron Imager

Pulse shape discrimination performances of single stilbene crystal, EJ-299-33 plastic and 6 Li loaded plastic scintillators have been compared. Pulse Gradient Analysis pulse shape discrimination algorithm has been tested for each scintillator sample, assessing their neutron/gamma separation. In this study each scintillator sample was irradiated with a 252Cf neutron source and, a real-time fast digitiser was used to collect the data. The figure-of-merit was utilised to compare the discrimination quality of the tested scintillator samples

Digital Neutron-Gamma Discrimination Performance of Stilbene in Comparison with Plastic Scintillators

No abstract available

Signal Noise Filtering Techniques in Radiation Detection Applications for Neutron Gamma Pulse Shape Discrimination

Neutron radiation often occurs as a result of radioactive decay and is accompanied by gamma radiation. This results in a mixed radiation environment comprising photons (gamma rays) and neutrons. Organic liquid scintillators are popularly used to detect both neutrons and gamma rays, where pulse shape analysis determines whether the event was caused by a neutron or a gamma-ray based on the decay characteristics of the pulse. Bespoke fast digitisers are currently widely used with organic liquid scintillators to record the pulse shape as digital samples. Pulse shape has high impact on pulse shape discrimination, especially in low energy region as it is generally difficult to discriminate a neutron event from a gamma-ray event. The quality of the discrimination of detected event is primarily determined by the quality of the pulse shape recreated using digital samples, as the discrimination is based on the characteristics of the pulse. The pulse signal is usually altered by signal noise and, the purpose of this paper is to select the best candidate for signal filtering technique to remove such high frequency noise components. It is important to ensure that the signal filtering technique is not consuming much of the processing power of the system and, it can be easily implemented in a real-time system

Organic Liquid Scintillators Based Source Localisation in Radiation Monitoring

No abstract available

Characterisation of a pixelated plastic scintillator for a coded aperture neutron/gamma imaging system

This paper experimentally investigates, the suitability of an organic pixelated plastic scintillator for a coded aperture neutron/gamma imaging system. The scintillator used in this study has been designed as a small scaled detector with an individual pixel size of 2.8 mm × 2.8 mm × 15 mm. Individual blocks of the scintillator have been separated from one another with ESR TM reflector foil to provide over 70% of optical isolation between pixels. Individual scintillator cells are arranged into 13×13 array with overall dimension of 39.52 mm × 39.52 mm. In this study the scintillator was attached to a single channel photomultiplier tube to assess its pulse shape discrimination capabilities. Initially the scintillator was irradiated with 137Cs gamma-ray source, and gamma-ray pulses were benchmarked with respect to a mathematical model. The detector was then irradiated with a spontaneous fission source, 252 Cf, and preliminary results suggested good pulse shape discrimination potential of the scintillator. It is believed, that it is the first time a small scale pixelated organic plastic scintillator has been tested in context of PSD capabilities for a coded aperture neutron/gamma imaging system

Estimating the Depth of Buried Radioactive Sources using Ground Penetrating Radar and a Gamma Ray Detector:2019 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), USNC-URSI 2019 - Proceedings

This study reports on nonintrusive depth estimation of a buried caesium-137 radioactive source using a ground penetrating radar (GPR) and a gamma ray detector. Specifically, the bulk density estimates from the GPR was used to fit a gamma ray attenuation model to the data from the detector. The depth of the source was successfully estimated when buried up to 18 cm in sand, gravel and soil. This will help in nonintrusive monitoring of nuclear contaminated sites

University Programmes during COVID-19 Pandemic

Within the physical sciences and other STEM-based disciplines, the need for physical, laboratory-based practical activities is essential to complement the more theoretical content associated with learning a subject. This entry reviews the transition from traditional to online/e-delivery that could be realised by educational providers when seeking to limit the spread of infection associated with viral pandemics (such as Covid-19), whilst remaining cognisant of the ability to retain a quality student learning experience and continue to achieve programme learning outcomes

Direct measurement of strontium 90 in groundwater: geometry optimisation of a photodiode based detector

This paper examines the feasibility of detecting strontium 90 in groundwater directly with photodiodes and considers the physical parameters which maximise radiation absorption within the detector. Geant4 simulations were used to draw comparisons between silicon, gallium arsenide and cadmium telluride detectors of varying surface area and thickness. Detectors were compared in their ability to absorb point and scattered sources of radiation. The results indicate that a detector, of 10 mm2 surface area, and 1 mm thickness offered the highest detection efficiency in a contaminated groundwater simulation. 1 mm thick and 100 mm2 detectors cadmium telluride and gallium arsenide detectors were modelled in a groundwater borehole scenario. Each material offered similar detection efficiency, but the greater backscattering effect in cadmium telluride resulted in a greater peak at lower energies compared to that observed in gallium arsenide

Study of modulation properties of tungsten based coded-aperture

The application of coded-aperture techniques for radiation imaging systems can be seen in various application fields, but the use of coded-apertures in mixed-field radiation detection in nuclear decommissioning remains largely unexplored. It is a key to understand the gamma-ray modulation properties of a tungsten based coded aperture, in order to explore the suitability of coded-apertures for mixed-field radiation detection systems. In this paper, an investigation into the gamma-ray modulation properties of a tungsten coded aperture is presented. The aperture was designed using the mathematical principles of Modified Uniformly Redundant Arrays (MURA). Due to the complexity of the design and the small size of individual cells, the aperture was built using additive manufacturing methods. The gamma-ray field was produced by 137Cs radioactive isotope at Lancaster University, UK. An organic plastic scintillator sample, which is capable of pulse shape discrimination, has been used to detect the gamma-ray field modulated by the tungsten aperture. The scintillator was energy calibrated using 137Cs and 22Na sources, before the first measurements of the modulated gamma-ray field were taken. The pulse shape discrimination performance of the scintillator was subsequently examined, using the mixed-field provided by 252Cf. In this study, each of 169 coded aperture cells were investigated by collimating the modulated gamma-ray field of 137Cs through a 25.4 mm thick lead supporting plate. The supporting plate has a single opening in the centre of the same dimensions as the single aperture cell 2.5 mm x 2.5 mm. The number of pulses detected for every aperture location were recorded in an array. The array was then used to create a two-dimensional image of the source, which was encoded through the coded aperture pattern. Finally, the image was decoded using deconvolution techniques to reveal the actual source location. Results obtained in the study indicate sufficient gamma-ray modulation properties of the aperture, despite the relatively small footprint and thickness of the coded apertur