Radiation instrumentation research is a cross-cutting area of research that impacts many areas of science and engineering. In particular, nuclear non-proliferation, our main application focus, is listed by the National Academy of Engineering as one of its grand challenges.
As a whole, our group’s research grants fund basic scientific research aimed at solving important problems including:
1) mobile sensing of penetrating radiations from radiological and nuclear threats during search operations
2) scanning containers for shielded nuclear materials– for cargo clearing, detection, and detailed characterization
3) ultrahigh resolution imaging at neutron science facilities worldwide
Highlights from six among our many projects are given below. Some information on other projects can be found by clicking on names on the People page and reading their brief bios. You are welcome to reach out to our people to learn more.
Investigation of DEtectors, Algorithms and Systems for Wearable Intelligent Nuclear Detection (IDEAS for WIND)
High-probability radiological interdiction requires a defense-in-depth strategy, as articulated in Homeland Security’s Global Nuclear Detection Architecture (GNDA). Local search capabilities, including wearable systems, are a critical component of this architecture. Current backpacked-based systems tend to be made from a combination of moderate resolution gamma ray scintillator (NaI(Tl)) and neutron detectors (He-3). A display unit gives the operator some indication of gross gamma and neutron counts for detection and localization, as well as some identification capability based upon the moderate resolution scintillator. Backpacks are more sensitive than the more commonly used handheld detectors (e.g., Identifinder), and they may be used, for example, in searches of city streets, high-rise buildings, or, less commonly, sea-going vessels/ships.
In our IDEAS our WIND program, we are performing basic research investigating the feasibility of different WIND designs that incorporate directionality, complex motion sensing, and object/source tracking. A proof-of-concept backpack will be built and demonstrated as a part of government characterizations. The hybrid, modular design will be sensitive to gammas and neutrons, and its design will be simple enough and cost effective to enable widespread deployment. Furthermore, newly developed machine learning algorithms for detection, localization, identification, online tracking, and advanced networking for WIND will be developed under this program, revolutionizing this data-driven application, adding layers of intelligence for robust and superior performance. The proposed work leverages our research experience and infrastructure in mobile RN detection, builds on successes throughout the research community, begins a new partnership with Pacific Northwest National Laboratory (PNNL), and is grounded in expert knowledge of the RN search mission space to ensure that the research conducted here will be academically and operationally impactful.
Investigation of DEtectors, Algorithms and Systems (IDEAS) for Rapid and Robust Clearing of Cargo from Shielded SNM
Detecting shielded SNM in full-size cargo is another essential part of the GNDA, especially since cargo represents 90% of world commerce. In this work, we are Investigating of DEtectors, Algorithms and Systems (IDEAS) for rapid and robust clearing of cargo from shielded SNM. In order to automatically and rapidly clear cargo containing high Z material with confidence, our algorithm approach exploits prior information, measured radiography data, and machine learning, building in just enough physics to make our online computation of active background both accurate and precise. Furthermore, we will also research and develop two detector systems to support rapid and robust cargo clearing as well as shielded SNM detection and identification, should the cargo fail to be cleared. Moreover, we will investigate innovative accelerator system advances that support more rapid cargo clearing while reducing dose delivered to lower Z regions of cargo. Our ideas have been brainstormed with cost in mind since the widespread deployment of rapid, effective radiography-based systems across the GNDA is essential. The proposed work starts a new engagement with Varian Medical Systems.
Our proposed computational work fits into a new scanning concept of operations for all cargo moving through ports of entry. This concept is expected to eliminate the need for secondary scanning while increasing the speed of radiography and reducing false negatives, especially cases where shielded SNM is present.
Investigation of detectors and algorithms for a trailer-based, neutron and gamma imaging system for mobile search of RN threats
In addition to handheld detectors and backpacks, trailer-based RN sensing systems are another important part of the Global Nuclear Detection Architecture. Such larger systems are more sensitive than backpack-based systems, and they may be used for detection and localization of RN threats that may be located tens of meters away from a roadway. Alternatively, they may be placed by the side of the road to function as an advanced portal-less portal monitor– or used for maritime chokepoint monitoring. In the past, trailer-based gamma imaging systems have been investigated and shown to be valuable for detection, localization and source tracking.
Our investigation combines gamma-ray and neutron imaging and spectroscopy system designs in order to improve upon the state-of-the-art in detection and localization of nuclear threat sources at ranges of order 100 m. In particular, this system is sensitive to Pu sources that are shielded by dense materials. A host of first-time innovations were explored through extensive simulations and measurements in order to put together a solution that integrates—for the first time— all available signals from shielded fissile materials. We have also using measurements to investigate systematic fast neutron background variations that are relevant for local area searches. For the first time, we measured systematic fast neutron background variations present in an urban area (downtown Knoxville) in order to understand how this affects our use of detection modalities during mobile search. As a part of this work, we built a trailer-based Dual Detection-Localization-Identification (DLI) proof-of-concept system (see gallery) as a part our Phase V demonstration work. We made measurements with the system while driving past neutron and gamma sources, and the measured data is now being analyzed. This project has been funded by the Department of Homeland Security through Oak Ridge National Laboratory.
Investigation of detectors and algorithms for tagged neutron interrogation systems
Scanning-based imaging systems are important for security at airports, ports, border crossings, and also as a part of international arms control and treaty monitoring. Our research group is advancing knowledge and understanding of a new multi-modal imaging technique capable of detecting and determining the properties of shielded HEU assemblies. A simulated result is shown at left, where the location of the fissile material (i.e., HEU) lights up in the tomograph of a complex object that includes gamma (Pb) and neutron (CH2) shielding.
Our work has resulted in an increased understanding of the fundamental physics limitations of fast, position-sensitive radiation sensors, with an investigative approach that is tailored to support this application. Our published peer-reviewed papers document this new understanding, which is now being applied to improving system performance parameters, including angular and timing resolution. The research approach includes both experimental and simulation work related to the system as a whole and two associated position-sensitive detectors, one of which is coupled to an interrogating neutron source. It is a multidisciplinary approach, drawing upon expertise in physics, nuclear engineering, electrical engineering, and materials science. The NSF and Homeland Security-funded project leverages recent advances in the medical imaging community as well as infrastructure and expertise at Oak Ridge National Laboratory. It incorporates a substantial amount of international collaboration in its attempt to push the state-of-the-art, and results have been presented at both international and domestic conferences. The UTK team working on this research includes three PhD-seeking students, a senior researcher, and an undergraduate student. Thanks goes to Paul Hausladen at ORNL who did the pilot work on this project, which came before our academic initiative.
A new project in this same general topic area has been funded by DOE NNSA. This work will focus on the development of new methods that have the potential to rapidly interpret images of uranium assemblies in real-time. Current developed methods utilize Monte Carlo calculations, which are accurate but impractical for use in the field. New methods develop extensions to the point kinetics model and address shielded uranium assemblies. Our work are doing is illustrated at left– imaged observables combined with measured time-correlated neutron data with the appropriate physics are expected to allow us to accurately estimate uranium enrichment and total uranium mass in an assembly.
Investigation of detectors, algorithms, and systems for high resolution radiography at neutron science facilities
This research topic is highlighted in an internal publication found here.
Neutron imaging is enabling the discovery of advanced materials for electrodes and electrolytes for the next generation energy storage systems, fuel cell membranes, carbon dioxide sequestration and radiation resistant self-healing. Several areas of research already benefit from neutron imaging, such as engineering, advanced material characterization, fluid-flow and/or two-phase flow devices, automotive technology, advanced manufacturing technology, aerospace, life and biological sciences, and national security applications. Neutrons are specifically well suited for imaging light atoms (e.g., hydrocarbons) buried in heavy atoms, and they are capable of characterizing the dynamics of fluid flow. In spite of all the success that neutron imaging has enjoyed in recent years, even higher-impact research is limited by the current temporal and spatial resolution of neutron detection devices.
In response, our group has been engineering solutions both for gaseous and scintillator-based He-3 replacement technologies in partnership with the Neutron Sciences Directorate at ORNL, and we are also in the midst of early work to help bring about the next generation of higher resolution systems (with goal of 1 micron!) that would impact advanced fuel cell development and diagnosis of cancer.
Our project funded by DOE Basic Energy Sciences is exploiting the recent developments in the area of optoelectronics with a goal to investigate and develop new concepts for position sensitive area detectors with orders of magnitude higher spatial resolution and higher temporal resolution and to demonstrate its capability to map the Li distribution in an operating Li-air cell (an important goal for our partner Hassina Bilheux at ORNL). Success in this research will be transformational to the field of neutron imaging and mesoscale science. It will also usher in faster detectors for energy selective imaging that would be possible at the high intensity pulsed neutron sources such as the Spallation Neutron Source, where VENUS, an imaging instrument, is being built for the worldwide scientific community. VENUS is due to be completed in three and a half years. The processes, knowledge and algorithms developed will allow for spatially (1 micron) and time resolved (~100 ns) high throughput neutron transmission imaging in large areas at reasonable costs in the near term. In addition to benefiting neutron imaging, these detectors will greatly benefit single crystal Laue diffraction for macromolecular research.
Non-scintillating glass detectors for sensing prompt gammas and gamma ray LIDAR
In this 5 year basic research effort completed in August 2014, we set out to discover the best properties and fabrication techniques of glass detectors that utilize Cherenkov emissions for sensing of penetrating radiations from fissile materials. The advancements supported counter-proliferation work by developing knowledge to enable the fabrication of low cost sensors with higher efficiency and adequate discrimination against background. The approach used was completely novel because other radiation detectors use for said purpose measure either the direct charge produced in radiation interactions, or indirect scintillation emissions. Over a hundred optically clear glass samples from 22 different families of glass formers were fabricated (see gallery), and their optical and radiation response was measured.
Our experimental investigations at the Idaho Accelerator Center explored prompt gamma backgrounds stimulated by high energy x-rays, and we presented the first work on a gamma ray time-of-flight-based nondestructive analysis technique that we call gamma ray LIDAR. Gamma ray LIDAR is of interest for NDA of single or multiple layers of moderate to high Z materials, e.g., cargo scanning. For example, the data at the lower left shows how well we were able to resolve a 4″ thick layer of lead (right peak) located 35 cm behind a 2″ layer of Fe (left peak) using a single backscatter view. This project was funded through the Defense Threat Reduction Agency and was carried out in partnership with Oak Ridge National Laboratory. Senior ORNL personnel included Lynn Boatner and Zane Bell. The UTK team included four graduate students, two postdoctoral researchers, and undergraduate students. Five peer-reviewed papers were published so far from this work.