Development of the Segmented Inverted Coaxial Germanium (SIGMA) Detector for Enhanced Gamma-Ray Spectroscopy and Imaging

Nuclear physics seeks to answer fundamental science questions such as "How did the universe begin and how is it evolving? How are stars born? What are the fundamental constituents and fabric of the universe and how do they interact? How can we explore and understand the extremes of the universe?" The aim of this research is to develop new technology that will allow scientists from the UK and international nuclear physics communities to investigate and address these key questions. A new type of radiation detector will be developed, SIGMA, which will provide a major advance in performance over current state-of-the-art systems.

The SIGMA detector will be able to locate gamma-ray interactions in space and time. This information will be used to track gamma-rays back to their point of origin, with unrivalled accuracy. The detector will be used alongside the AIDA system, which will detect another type of radiation, beta particles. This system is already under development by UK nuclear scientists at the Universities of Edinburgh and Liverpool and at STFC Daresbury Laboratory. Future nuclear physics experiments will combine the information from both detection systems to facilitate the collection of high-quality data at international facilities. This technique is set to significantly enhance these experiments, where as little as a few nuclei of interest are produced in a day.

The long-term plan is that several SIGMA detectors will be deployed as part of the DESPEC experiment at the FAIR facility in Germany, where many UK scientists will conduct their research. In this experiment, the detectors will be used to measure key properties of nuclei that have never been observed before, to provide a deeper understanding of how stars are born and how they evolve. Development of the SIGMA detector is of high strategic importance to the STFC UK nuclear physics and is timely, with the FAIR facility coming online from 2019.

A secondary aim of this research is to evaluate the suitability of the SIGMA detector for deployment as a gamma-ray imaging system for commercial and industrial applications. The detector would revolutionise performance in a variety of applications such as nuclear decommissioning, security, environmental monitoring and medical imaging. For example, using the detector in nuclear medicine would enhance quality of life and health through earlier diagnosis of cancer and neurological conditions. The detector could also be operated in national security and defence. For example, it could be used to image gamma-ray maps from spent fuel from nuclear reactors on board Royal Navy submarines. Data acquired from such a system would be used to inform models that underpin the safe design of future reactors.

A direct spin-off from this research is in gamma-ray imaging and there are many potential beneficiaries outside the academic community. A spectroscopic gamma-ray imaging device such as the SIGMA detector, would open existing markets worth in excess of £100M pa to UK companies, covering medical, national security, science, industrial, and defence. The SIGMA detector could be operated as a single-detector gamma-ray imaging device with high efficiency and excellent image quality. There are a wide variety of end-users and the beneficiaries are equally as diverse.

Employing the detector as a gamma-ray imaging system in nuclear medicine would provide societal benefits, as quality of life and health could be enhanced through earlier diagnosis of cancer and neurological conditions. In parallel, reduced medical imaging procedure times would improve the throughput of NHS procedures. The beneficiaries of the application of this research in medicine are therefore the public and the NHS.

The SIGMA detector could be operated in national security and defence. For example, it could be used to image gamma-ray maps from spent fuel from nuclear reactors on board Royal Navy submarines. An investigation is already underway at the University of Liverpool, in collaboration with the ministry of defence, to evaluate gamma-ray imaging techniques using germanium detectors. Data acquired from such a system would be used to inform models that underpin the safe design of future reactors. Direct beneficiaries of this research would be the Royal Navy and those concerned with national defence.

A long-term objective of the project is to develop a proposal in collaboration with industry for future exploitation of the gamma-ray imaging capability, with the opportunity for significant economic and societal impact. The gamma-ray imaging system would be of interest to a company that has adjacent positions in both technologies and markets. Canberra is a world-leading supplier of instrumentation for the nuclear industry and their primary markets are in the areas of radiological safety and security. They are therefore ideally positioned to collaborate on the long term-objective of commercialising gamma-ray imaging with the SIGMA detector, for safety and national security applications. In typical safety and security applications, the location of the source is not necessarily known and the radionuclide of interest may be masked by the presence of other radiological nuclides. Current approaches in these applications are to collimate a detector to be able to localise the direction of gamma-ray radiation. This reduces the sensitivity of the systems and requires longer measuring times, which increases personnel exposure and increases the risk of misidentifying materials. The SIGMA gamma-ray imaging detector would overcome these limitations, which would impact on the safety of those working in the nuclear industry and would have economic impact by improving the throughput of these measurements.

The nuclear physics groups at Liverpool and Daresbury have experience on collaborating on and producing output from projects that deliver impact outside of academia. They disseminate the output of their research to other academics, the public, employees of the nuclear industry and healthcare professions. For the academics and industrial experts, our research will continue to be showcased at UK and international conferences and meetings. The University of Liverpool hosts many events for schools aimed at promoting physics, and in particular a series of nuclear physics masterclasses for year 12 pupils twice a year. These benefit from the nuclear physics expertise in the group and its excellent laboratory facilities where this project will take place. We will go to to schools to deliver lectures on nuclear physics and its applications, such as gamma-ray imaging with the SIGMA detector.