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AbstractMachine learning has been found to be ubiquitously useful across many industries, presenting an opportunity to improve radiation detection performance using data-driven algorithms. Improved detector resolution can aid in the detection, identification, and quantification of radionuclides. In this work, a novel, data-driven, unsupervised learning approach is developed to improve detector spectral characteristics by learning, and subsequently rejecting, poorly performing regions of the pixelated detector. Feature engineering is used to fit individual characteristic photo peaks to a Doniach lineshape with a linear background model. Then, principal component analysis is used to learn a lower-dimension latent space representation of each photo peak where the pixels are clustered, and subsequently ranked, based on the cluster mean distance to an optimal point. Pixels within the worst cluster(s) are rejected to improve the full-width at half-maximum (FWHM) by 10% to 15% (relative to the bulk detector) at 50% net efficiency when applied to training data obtained from measurements of a 100 μCi 154Eu source using a H3D M400i pixelated cadmium zinc telluride detector.These results compare well with, but do not outperform, a greedy algorithm that accumulates pixels in order of FWHM from lowest to highest used as a benchmark. In the future, this approach can be extended to include the detector energy and angular response. Finally, the model is applied to newly seen natural and enriched uranium spectra relevant for nuclear safeguards applications. [ABSTRACT FROM AUTHOR]

Liquid crystals (LCs) can be promising for detection of ionising radiation (IR). However, there is little information about their interaction with IR and there are no systemic studies of the dosimetric application of LCs. In this communication, we show for the first time the capabilities of a new type of radiation detector – cholesteric liquid-crystalline dispersion (CLCD) of DNA obtained using polyethylene glycol (PEG) and salt indued condensation. Irradiation of the DNA CLCD samples with 0–100 kGy of 7.6 MeV bremsstrahlung led to significant change in their circular dichroism (CD): ≈5% and ≈12% increase in the signal was observed at 10 and 20 kGy, while in the range of 20–90 kGy the CD signal decreased linearly. Thus, detectors based on DNA CLCD could be of interest for such application of IR as material modification or radiation sterilisation. At the same time irradiation can help to stabilise dispersion particles and can be used to prevent their sedimentation. Unirradiated samples degraded within 24 h after preparation, while the irradiated ones were able to maintain the intensity of CD signal for more than 168 h.Schematic representation of the dual effect of radiation exposure the DNA CLCD. [ABSTRACT FROM AUTHOR]

Recent research has focused on the development of surrogate models for radiation source localization in a simulated urban domain. We employ the Monte Carlo N-Particle (MCNP) code to provide high-fidelity simulations of radiation transport within an urban domain. The model is constructed to employ a source location ( x , y , z) as input and return the estimated count rate for a set of specified detector locations. Because MCNP simulations are computationally expensive, we develop efficient and accurate surrogate models of the detector responses. We construct surrogate models using Gaussian processes and neural networks that we train and verify using the MCNP simulations. The trained surrogate models provide an efficient framework for Bayesian inference and experimental design. We employ Delayed Rejection Adaptive Metropolis (DRAM), a Markov Chain Monte Carlo algorithm, to infer the location and intensity of an unknown source. The DRAM results yield a posterior probability distribution for the source's location conditioned on the observed detector count rates. The posterior distribution exhibits regions of high and low probability within the simulated environment identifying potential source locations. In this manner, we can quantify the source location to within at least one of these regions of high probability in the considered cases. Employing these methods, we are able to reduce the space of potential source locations by at least 60%. [ABSTRACT FROM AUTHOR]

The nuclear accident at Fukushima, which led to the release of radioactive fallout over densely populated areas, highlights a broader problem: What is the best way for the public to detect and monitor radiation levels in urban areas before, during, and after a major radiological event? The authors describe a system that would incorporate inexpensive radiation detectors in mobile phones equipped with the capability of continuously transmitting data to a central server. This server would correlate data from a large number of detectors carried by people moving randomly in an urban environment, locating fallout hot spots and illicit radiological sources carried by terrorists. The authors discuss both technical aspects of the system and some practical issues involved in implementing it, including cost. [ABSTRACT FROM AUTHOR]

International concern over nuclear terrorism has grown during the past few decades. This has driven a broad spectrum of efforts to strengthen nuclear security globally, including the widespread adoption of radiation-detection technology for border monitoring. Detection systems are now deployed at strategic locations for the purported purpose of detecting and deterring the smuggling of nuclear and radioactive materials. However, despite considerable investment in this area, few studies have examined how these programs are implemented or the operational challenges they face on a day-to-day basis. This article seeks to address this with a focus on radiation-detection efforts at maritime facilities. Utilizing practitioner interviews and a survey, this article identifies the factors that influence the planning and use of these systems in this fast-moving environment. The results clearly demonstrate that the implementation of these systems varies significantly across different national and organizational contexts, resulting in a fragmented global nuclear-detection architecture, which arguably undermines efforts to detect trafficked nuclear-threat materials. Greater consideration should therefore be given to developing international standards and guidance, designing and adopting tools to support key parts of the alarm assessment process, and broader sharing of good practice. [ABSTRACT FROM AUTHOR]

Semi-insulating Gallium nitride was irradiated by fast and thermal neutrons with fluences from 1014to 1016 n/cm2. Depth-resolved cathodoluminescence spectroscopy was used to determine defects changes before and after irradiation. The results revealed two kinds of defects affected near-band emission recombination from two opposite directions. One was attributed to irradiation-induced N vacancies that contribute to near-band emission recombination. Another was attributed to irradiation-induced deep level defects that contribute to sub-band gap recombination and thus decrease the near-band emission recombination. [ABSTRACT FROM AUTHOR]

The RadBall is a 140-mm (5.5-in.)-diam deployable, passive, nonelectrical gamma hot-spot imaging device that offers a 360-deg view of the deployment area. The device is particularly useful in instances where the radiation fields inside a nuclear facility are unknown, but a suitable decommissioning strategy is required to be planned. The original version of the technology had a number of drawbacks including a relative insensitivity to radiation (at least 3 Gy required), which led to long deployment times, as well as a narrow target dose range (3 to 8 Gy ), which meant that the user required prior knowledge of the radiation fields in which the device was to be deployed. The United Kingdom's National Nuclear Laboratory has developed the technology to overcome both of these issues. The developments associated with the new technology are described here, as are some recent tests undertaken at the Sellafield facility in the United Kingdom. The work has resulted in a significant improvement in sensitivity--150 times--as well as greatly widened the target dose range to between 20 mGy and 50 Gy. The new version of the technology therefore has a much-improved applicability compared to the original technology. [ABSTRACT FROM AUTHOR]

In this article, the feasibility of using CsTb2F7 crystals as scintillating detectors to build radioluminescent fiberoptic dosimetry (FOD) probes has been investigated for the first time. The radioluminescence (RL) efficiency of this compound has been found to be more than twice as high as that of commercial Al2O3:C detectors under excitation with gamma radiation from a 60Co source. Additionally, the intensity of the RL signal shows no dependence on the accumulated dose. Both RL and photoluminescence spectra are nearly identical, showing emission bands at 490 and 550 nm and a minor band at 600 nm, which are compatible with the characteristic emission of Tb3+. In accordance with these results, stoichiometric terbium fluoride seems to be a promising material for use as an RL sensor for FOD in radiation medicine. [ABSTRACT FROM AUTHOR]

Over the past decade there has been a growing interest in the application of a class of gaseous radiation detectors, known generally as micropatterned devices, for radiation protection dosimetry and monitoring. The purpose of this paper is to review the features of micropatterned devices that make them of particular interest and to report on some of the successful applications in radiation protection dosimetry and monitoring of instruments based on these detectors. Micropatterned devices, originally developed within the high-energy physics research community, are of several different types and design. The principal devices that have found application in radiation protection measurement science are gas microstrip detectors, gas electron multipliers, and micromesh gaseous structures. The operation of these devices will be reviewed along with modifications that have been carried out to make them suitable for radiation monitoring and microdosimetry. [ABSTRACT FROM AUTHOR]