There are a number of measurement techniques employed to enforce the Comprehensive Test Ban Treaty (CTBT), with complementary measurements of seismic and atmospheric radionuclide data being foremost. The potential for decoupling and trapping of radionuclide gases in underground nuclear tests places importance on the identification and characterization of new techniques. Earlier studies of...
Applications for accurate reconstructions from Passive Radiation Imaging are widespread from medical imaging to security. Unfortunately reconstructing such images are often ill-posed problems and require regularization to make sense of them. One recently developed regularizer known as Multibang makes use of a priori information about the possible attenuation values in an object to both improve...
Typical radiation detectors used in portal scanning employ plastic scintillators to effectively and inexpensively cover large areas.
To optimise performance the spectral range of scintillation should correspond to the maximum sensitivity of the photodetector.
Wavelength shifters can be employed to enhance this correlation but can be at the expense of scintillation efficiency.
Quantum dots have...
A detecting element which consists of a dense colloid suspension of nanoparticles is sensitive to ionising radiation both particulate and electromagnetic; at room temperature. The detector output is measured directly as a voltage and does not require intermediate photon detection. A large detecting surface area increases the probability of interaction between radiation and detector. The...
X-ray sources are used in radiography in order to scan cargo coming through ports around the world in much the same way as x-ray machines in hospitals. Additionally, knowledge of nuclear physics allows not just the shape, but the material properties of the objects to be determined by such scanners. All such scanners involve generating x-rays using electron beams which could potentially be...
This project compared the current wavelength shifting fibres used in SoLid to the proposed wavelength shifting strips. The relative light yield of the strips compared to the fibres was investigated, and the results seem to indicate that the strips are at least as good, if not marginally better than, the current fibres. However taking into account the relatively crude methods involved in using...
In recent years, there has been a surge in the number of academic research groups and commercial companies exploiting cosmic-ray muons for imaging purposes in a range of applications. Typically, these involve shielded containers and/or large, complex structures that cannot be investigated using conventional imaging techniques. Many of these applications relate to nuclear security and...
The discovery of semiconducting polymers was followed by a rapidly growing commercial interest for many applications in electronic devices (polymer light-emitting-diodes, field-effect-transistors, polymer solar cells etc.) but not as much in the field of ionising radiation detection. The aim of the research presented here is the fabrication of an organic, semiconducting sensor for neutron...
In this paper we discuss developments in pulse shape discriminating plastic scintillators for neutron-gamma separation. Three independent PSD sensitive detectors were constructed and tested, providing typical ?figures of merit of 1.09 at 1 MeVee.
Pulse Shape Discrimination (PSD) is the process of distinguishing between radiation types such as neutrons or gamma-rays. Dual detector scintillators can be used as they fluoresce from both neutron and gamma-ray interactions. Once the light has been collected on the photo sensor and its electric signal gets digitised, discrimination algorithms can be applied to identify the radiation type on a...
This contribution is currently undergoing the AWE's clearance process.
Several isotopes of natural and man-made radioactive materials give off only alpha radiation, and although easily stopped by skin, ingestion of alpha particles is most hazardous to humans. It is, therefore, most important that detectors capable of detecting the presence of alpha emitting materials are available for use in the field, either for routine nuclear operations, accidental...
This project focuses on exploring one of the most advanced light sensors coupled to bright scintillator detectors, which are used for detecting ionizing radiation. This novel device, which has been initially developed by the University of Edinburgh for improving the sensitivity of positron emission tomography using a time-of-flight correction, can also enable a whole new generation of...
Highly sensitive neutron detectors with directional information could improve the timeliness of detection and localisation of special nuclear material (SNM) at national ports of entry and for deriving operational and protection quantities in the field of neutron dosimetry.
In this context, two neutron source localisation algorithms, for use with a novel plastic segmented scintillator...
Detecting radioactivity is inherently uncertain. In a typical passive detection scenario (e.g. scanning cargo coming off a ship), a large number of factors need to be taken into
account, all of which can be subject to varying levels of uncertainty. For example, sensor count rates can vary, cargo can contain benign sources of radiation (e.g. bananas or tiles) that could mask other proscribed...
Antineutrinos offer new possibilities for nuclear safeguards. Their abundant production in on-line fission reactors and the near impossibility of shielding them presents an opportunity for non-invasive on-line reactor monitoring. In support of this there have been numerous predictions of reactor antineutrino emissions, both based on the work of Schreckenbach et al and ab initio methods...
Accurate automated characterisation of radioactive material is crucial for applications in decommissioning and the detection of illicit material. While detection hardware rarely changes outside of bespoke solutions, improvements in Radio-isotope~IDentification (RID) algorithms have become a significant research focus. A generalised gamma simulator has been built using the GEANT4 toolkit to...
Portal monitors for use in nuclear security typically use large volume detectors such as plastic scintillator detectors fabricated from polyvinyl toluene (PVT). Recent advancements in plastic scintillators have produced new scintillator materials which respond to both neutron and gamma radiation. These materials show pulse shape discrimination (PSD) properties which can b used to
distinguish...
The detection and discrimination properties of two different plastic scintillator detectors were investigated, namely one constructed from standard plastic scintillator and another of the same scintillator doped with Gadolinium. The response of these detectors to exposure to neutrons and gammas from 137Cs and 252Cf sources is assessed.
Explosives can be detected by the neutron activation of nitrogen present
in the material. Conventionally, inorganic scintillators are used, but in
order to detect the characteristic 10.8MeV emission with any efficiency,
large volume detectors are required. Lead glass cherenkov detectors have
been constructed as an alternative to conventional inorganic scintillators.
Such detectors are...
EJ-270 is a 6Li loaded PVT-based plastic scintillator developed by Eljen Technologies and Lawrence Livermore National Laboratories. The 6Li makes it sensitive to thermal neutrons and pulse shape discrimination (PSD) can be utilized to separate the neutron events from γ-ray events. The low cost, large available volumes and environmental stability of EJ-270 makes it an attractive alternative to...
A liquid scintillator fast neutron detector has been built at Sheffield Hallam University, which can improve neutron spectrometry for homeland security. This ambitious project utilises an EJ-331 (gadolinium loaded liquid scintillator), which permits differentiation between neutron, gamma and charged particle radiation, and allows the energy of the incident radiation to be determined. The...
Novel Perovskite X-ray/Gamma Detectors and Potential Applications
X-ray imaging has been the mainstay of non-invasive diagnostics in fields such as medicine, security and defence, non-destructive testing and production line quality control. The development of new detectors that offer greater sensitive, energy resolution, radiation hardness and mechanical robustness continues to be a...
Peak Identification in Low-Resolution γ-ray Spectra Using the Cosine Similarity Measure
M. Nakhostin and P. J. Sellin
Department of Physics, University of Surrey, Guildford, GU2 7XH, UK
Automated identification of radioisotopes through γ-ray spectroscopy with low-cost γ-ray detectors such as NaI(Tl) is of great interest for applications such as nuclear security, nuclear emergency, and...
In this paper, A 6x6x76.2mm CsI:Tl crystal coupled to two SiPMs at each end and coated with PTFE, high reflective 3M and black tape were prepared and tested. Energy and spatial resolution of the three detectors were measured and the effect of the coating material on the interaction position was investigated. Spatial resolution measurements were carried out using a computer motorized scanning...
In this project, we have measured and studied the pulse shapes of signals originating from inorganic scintillators
coupled to Silicon Photomultipliers for a varying temperature. In particular, we performed measurements for
CsI, NaI, CeBr3 and CLYC scintillating crystals. The measurements took place inside a controlled atmosphere
station that allowed handling of the bare hygroscopic crystals....
The use of organic semiconductors as radiation detectors is a new organic electronics research. A particularly valuable tool to aid development of such devices is an emerging trend in reliable simulation that can be used to predict behaviour. We present a simulation program that was developed to investigate how organic materials react to incident radiation, and reconstruct electronic signals...
We report steady state 5.49 MeV alpha particle detection results using organic semiconductor diodes fabricated using a blend of poly(3-hexylthiophene) and phenyl-c61-butyric acid methyl ester, under modest bias conditions (up to ±20 V). Alpha particle device sensitivities between 10^4 and 10^7 nC mGy^-1 cm^-3 are achieved (depending on individual device and drive conditions). The alpha...
We propose a framework for nuclear element detection, using spectral X-ray CT, that utilises discrete tomography and machine learning algorithms to detect the inclusion of targeted materials within a sample. Assuming knowledge of a nominal list of materials and spectral CT data from a small number of angles, the proposed method proceeds to image and classify the materials using their known...
The europium-doped strontium iodide (SrI2:Eu) scintillator was first discovered in 1968 by Hofstadter [1]. In recent years, owing to the significant improvements in the technology of crystal grow of this scintillator, it has emerged as a strong candidate for gamma-ray spectroscopy applications [2]. This crystal exhibits extremely high light yield, proportional response, and very low level of...
This poster details the outcome of the NuSec Netwowrk Summer 2016 Pilot Project which investigated the use of Thallium Bromide as a room temperature semiconductor detector. With the help of NuSec funding a functional gamma ray detector was developed, utilising a Thallium Bromide crystal, that ultimately gave spectroscopic performance comparable to current market detectors. Applications
of...
The Verification Instrument for the Direct Assay of Reactors at Range (VIDARR) is a reactor monitoring tool based on solid plastic scintillator. Reactors produce c. 10^20 anti-neutrinos per gigawatt (thermal). These anti-neutrinos can then be captured by protons in the detector via inverse beta decay (IBD). This produces a distinct double coincidence signal in the VIDARR detector. The GEANT4...
