Aerosol science, the study of airborne particles from the nanometre to the millimetre scale, has been increasingly in the public consciousness in recent years, particularly due to the role played by aerosols in the transmission of COVID-19. Vaccines and medications for treating lung and systemic diseases can be delivered by aerosol inhalation, and aerosols are widely used in agricultural and consumer products. Aerosols are a key mediator of poor air quality and respiratory and cardiac health outcomes. Improving human health depends on insights from aerosol science on emission sources and transport, supported by standardised metrology. Similar challenges exist for understanding climate, with aerosol radiative forcing remaining uncertain. Furthermore, aerosol routes to the engineering and manufacture of new materials can provide greener, more sustainable alternatives to conventional approaches and offer routes to new high-performance materials that can sequester carbon dioxide. The physical science underpinning the diverse areas in which aerosols play a role is rarely taught at undergraduate level and the training of postgraduate research students (PGRs) has been fragmentary. This is a consequence of the challenges of fostering the intellectual agility demanded of a multidisciplinary subject in the context of any single academic discipline. To begin to address these challenges, we established the EPSRC Centre for Doctoral Training in Aerosol Science in 2019 (CDT2019). CDT2019 has trained 92 PGRs with 40% undertaking industry co-funded research projects, leveraged £7.9M from partners and universities based on an EPSRC investment of £6.9M, and broadened access to our unique training environment to over 400 partner employees and aligned students. CDT2019 revealed strong industrial and governmental demand for researchers in aerosol science. Our vision for CDT2024 is to deliver a CDT that 'meets user needs' and expands the reach and impact of our training and research in the cross-cutting EPSRC theme of Physical and Mathematical Sciences, specifically in areas where aerosol science is key. The Centre brings together an academic team from the Universities of Bristol (the hub), Bath, Birmingham, Cambridge, Hertfordshire, Manchester, Surrey and Imperial College London spanning science, engineering, medical, and health faculties. We will assemble a multidisciplinary team of supervisors with expertise in chemistry, physics, chemical and mechanical engineering, life and medical sciences, and environmental sciences, providing the broad perspective necessary to equip PGRs to address the challenges in aerosol science that fall at the boundaries between these disciplines. To meet user needs, we will devise and adopt an innovative Open CDT model. We will build on our collaboration of institutions and 80 industrial, public and third sector partners, working with affiliated academics and learned societies to widen global access to our training and catalyse transformative research, establishing the CDT as the leading global centre for excellence in aerosol science. Broadly, we will: (1) Train over 90 PGRs in the physical science of aerosols equipping 5 cohorts of graduates with the professional agility to tackle the technical challenges our partners are addressing; (2) Provide opportunities for Continuing Professional Development for partner employees, including a PhD by work-based, part-time study; (3) Deliver research for end-users through partner-funded PhDs with collaborating academics, accelerating knowledge exchange through PGR placements in partner workplaces; (4) Support the growth of an international network of partners working in aerosol science through focus meetings, conferences and training. Partners and academics will work together to deliver training to our cohorts, including in the areas of responsible innovation, entrepreneurship, policy, regulation, environmental sustainability and equality, diversity and inclusion.

This knowledge exchange project seeks to develop an optimised Cadmium Zinc Telluride (CZT) system for low dose molecular breast imaging (MBI). Breast cancer is the most common type of cancer in the UK, with 1 in 8 women developing the disease. Approximately 50% of women of screening age have mammographically dense breasts but conventional X-ray mammography has reduced diagnostic performance for these patients. This limitation can be overcome by using MBI, a technique in which a molecular tracer selectively targets malignant breast tissue to provide high-resolution functional images. Earlier diagnosis and more accurate staging of the disease using optimised MBI systems will potentially lead to better patient outcomes and reduced mortality rates. The proposed research will improve the imaging performance of MBI, which will increase the probability of detecting lesions in the breast. This will be based on exploiting our knowledge of how radiation interacts in the imaging system.

Conventional medical x-ray imaging systems are equipped with: i) a powerful x-ray tube, mounted on a fast rotating gantry, which generates polychromatic radiation characterised by a broad spectrum of energies, and ii) an x-ray detector, which records the total energy of all the x-rays that transmitted through the body of the patient. The attenuation of the x-ray beam, as it passes through the patient's body, depends on the photon energy and this energy dependence is different for different materials, tissues and elements. Therefore, the energy of each detected photon contains additional valuable information about the elemental composition of the scanned object. The current x-ray detectors are mostly insensitive to this spectral information, because their signal output is proportional to the total energy deposited within the active area of the detector, while a detector with energy-discrimination capabilities can provide the solution for enhanced exploitation of this additional spectral information by recording all these different energy photons and arranging them into respective spectral bins. Direct conversion CdZnTe (CZT) semiconductor detectors with high sensitivity, high stopping power, high spatial resolution and excellent energy resolution have emerged as the dominant solid-state room temperature detectors in a wide range of spectroscopic and imaging applications. Most recently, there has been a growing interest in using the CZT detectors for the next generation of high-flux multi-energy x-ray imaging systems, with a particular emphasis on Computed Tomography (CT) and 3D x-ray breast imaging. Both these imaging modalities have common goals, the ability to make quantitative measurements, and therefore, the enhancement of diagnostic capability at low patient doses. However, these applications require very fast data acquisition, and hence, there is a need for detectors that can efficiently operate at a high photon flux, almost 100 million photons per second per square millimetre. The design and fabrication of energy-sensitive CZT detector arrays for high-flux photon-counting multi-spectral x-ray imaging pose significant technological challenges and issues, which are the focus of the investigations of this proposal. The main objectives of this project are: 1. the innovative design specifications of a photon-counting CZT detector for high-flux multi-energy x-ray imaging; and 2. the optimum architecture of a proof-of-concept photon-counting spectral x-ray imaging system based on optimised CZT detectors for multi-energy x-ray spectral CT and 3D x-ray breast imaging. The main motivation of this work is to investigate to which extent photon-counting, energy discriminating CZT detectors are capable of overcoming fundamental performance limits and carrying out quantitative imaging revealing the additional spectral information, and therefore, improving conventional x-ray medical imaging. If energy information is recorded alongside the intensity, x-ray medical imaging modalities could increase diagnostic accuracy through soft-tissue differentiation, material decomposition, tumour characterisation, target quantification and development of disease-specific targeted contrast agents and drugs. The latter could improve low-contrast resolution and overall image quality at significantly reduced radiation doses and lead to superior diagnostic performance with lower cost. Spectral x-ray imaging can become an important imaging technique providing material-specific quantitative information in combination with high spatial resolution imaging, and therefore, leading to a paradigm shift in x-ray medical diagnostics.

Nowadays numerous applications are employing ionising radiation as a non destructive probe to obtain information that is not available through visual inspection. These applications range from medical imaging to industrial tomography and homeland security as well as archeometry and history of art. Furthermore, ionising radiation plays a key role in the quest for answering a wide range of fundamental physics questions. There are numerous examples of large-scale physics experiments around world to probe, for example, nuclear structure, particle physics or astrophysics through measurements with ionising radiation. Driven by these demanding applications and fundamental research, the technology for detecting ionising radiation has seen a remarkable progress in recent years. This progress, however, has occurred in many cases in academia and industry in parallel and the transfer of knowledge between them has been limited. There is a great potential gain and impact in building strong bridges between the two communities that will facilitate the knowledge transfer. In this particular project we are interested in transferring the technology on position sensitive scintillator detectors and their use in gamma-ray imaging. This state-of-the-art technology has been developed within the academic community and is already being used in fundamental physics experiments. The transfer of this technology to industry will enable applications employing gamma-ray detection to reach a higher level of sensitivity and in particular it will impact directly areas such as medical imaging and nuclear security.

Transuranic elements like Plutonium are radioactive materials which spontaneously emit neutrons. A neutron detector is therefore a crucial tool to detect illicit trafficking of radioactive materials that could be used to make nuclear or dirty bombs. It is also an important tool for radio-protection at nuclear facilities. Currently most neutron detectors in use are based on Helium-3 gas tubes. The current shortage of Helium-3 means that the supply can no longer meet the demand. Alternative technologies are needed in order to replace Helium-3 systems already deployed. This project aims to replace successfully Helium-3 detectors used as hand held and backpack system by a new technology based on layers of neutron sensitive material mixed with highly efficient scintillator. The technology is easily scalable and the design flexible enough to meet a wide range of detector requirements.