Fusion is the process that powers the sun. If we can harness fusion power on Earth, it would provide effectively limitless, carbon-free, safe energy. There are two approaches. In inertial fusion energy (IFE), high power lasers (or other 'drivers') compress a pellet of frozen deuterium-tritium fuel to very high density and temperature, confined for short times associated with the fuel's inertia (nanoseconds). The other approach, presently the more advanced, is magnetic fusion energy (MFE). Here the hot, low density fuel is held in a toroidal chamber using magnetic fields for confinement times of seconds. When the fuel is heated to fusion temperatures (100,000,000K), the electrons are stripped from the nuclei, creating an ionised gas called a plasma. Plasmas are susceptible to a range of waves and instabilities that drive turbulence and degrade confinement. In MFE this determines the device size. For example, the 16Bn Euro ITER facility is large enough to give the required confinement despite the turbulence, providing a fusion yield of 10 times the applied heating power. Scheduled for completion in 2020, ITER will provide the first plasma with heating dominated by the energetic alpha particles produced by the fusion reactions, allowing the final physics questions to be answered to build a demonstration power plant, DEMO. For example, how do the alpha particles affect the plasma stability and turbulence, and how do we exhaust them from the plasma once they have cooled to avoid dilution extinguishing the fusion burn? The other fusion product is a 14MeV neutron to be captured in a blanket to extract its energy and react it with lithium to produce tritium. Understanding how materials behave under this energetic neutron irradiation, combined with exposure to hot plasma, is something we still know little about because ITER will be the first device to create these conditions. ITER will also address a range of fusion technologies, such as heating systems, tritium breeding blankets and exhaust handling: issues that integrate plasmas with materials. The flagship IFE facility is NIF in the US. It tried to achieve fusion conditions during 2012, but did not succeed. The reasons require more research, but again plasma instabilities are a likely cause. Once the issues at NIF are resolved the priorities for future laser-based systems (e.g. HiPER) can be defined on the route to inertial fusion energy. Then the materials issues discussed above for MFE apply to IFE also. IFE creates extreme states of matter with high energy density that have important applications beyond energy. One is to create conditions suitable for benchmarking the computer codes that contribute to the UK's nuclear deterrent, avoiding the need for weapons testing: important in the strategy to avoid proliferation. AWE has recently commissioned a large laser facility, Orion, primarily for this purpose. Fusion research interfaces with several fields. There are synergies with the nuclear industries where the next generation fission reactors will have high energy neutrons and so share some materials issues with fusion. Space plasmas share phenomena also found in MFE plasmas while energetic astrophysical phenomena can be simulated in the lab using high power lasers. In industry, low temperature plasmas with similar characteristics to those at the edge of a MFE plasma have applications in manufacturing, from advanced coating technologies to computer chips. The focus of our CDT is fusion, training 5 cohorts, each of 15-16 PhD students, across the range of plasma, materials, IFE and MFE, as well as related fusion technologies. This will position the UK to take advantage of new high power laser and MFE facilities, advancing fusion energy. IFE, along with lab astrophysics, will develop skills relevant to the UK's national security strategy. Our training programme will seek to benefit other students in related fields, such as technological plasmas and nuclear materials.

As energy demand increases and the impacts of climate change worsen, fusion offers the prospect of abundant, agile, low-carbon, baseload supply. During the next five years, fusion reaches a defining period. ITER - a ~20BnEuro megaproject that will demonstrate fusion is possible on a commercial scale - begins operation, whilst JET - for forty years the world's premier fusion facility - ceases operation. In parallel, governments and private investors are funding fusion powerplant design driven by the imperative to address climate change. The UK government stated that the UK has a 'moral responsibility to lead on climate change', having legislated to deliver 'net-zero' greenhouse gas emissions by 2050, committing to "doubling down on our ambition to be the first country to commercialise fusion energy technology" by establishing the STEP programme to build a prototype compact powerplant by 2040. The UK has also associated to the Euratom Research programme, remaining a full participant in ITER and the EUROfusion DEMO programme, the world's largest powerplant design effort, targeting fusion electricity 20 years after ITER begins high power operations. Whilst STEP and DEMO are comprehensive powerplant design programmes, there are considerable technical uncertainties without known solutions that must be overcome in parallel. This proposal will address these science and technology challenges, innovating to make designs easier and cheaper, reducing uncertainties in design, working with world-leaders from other sectors to exploit digital design methods that accommodate inherent uncertainty, and developing powerful new models based on fundamental theoretical developments. This differs from normal development paths - where the underlying science is resolved before the design proceeds or where small-scale demonstrators are possible - and thus presents very deep challenges: How can robust choices be made in the face of considerable uncertainty? How do we bridge the gaps between feasible experiments and the environment inside a powerplant, when empirical demonstrations are too slow and costly? How do we proceed without experimentally substantiated solutions in each discipline of an integrated design? This programme will confront these questions with multi-disciplinary research and innovation that builds on the UK's unique breadth of capability in fusion, targeting fundamental advances in the most demanding technical challenges: a) The confinement of a fuel at 150 million degrees over long timescales - we will lead the final high-power experiments in JET for ITER; b) The exhaust of excess heat at levels well above those experienced by a re-entrant spacecraft - we will test a novel exhaust solution on MAST Upgrade and develop new high-performance models to bridge the gap from MAST-U to a powerplant; c) The resilience of materials which will surround the most intense neutron source on Earth - our Materials Research Facility will enable examination of irradiated materials properties to test and develop world-leading models of materials behaviour; d) The ability to design, manufacture and qualify fusion components without a full demonstrator plant - with industry, this programme will target new advanced manufacturing techniques and testing capabilities in our new Fusion Technology Facilities; e) A solution to breed, extract, use and recycle the necessary inventory of tritium with minimal loss and accurate accounting - the new H3AT facility will enable development and demonstration of tritium systems at a representative scale; f) The requisite availability to produce a viable cost of electricity - we will develop novel maintenance solutions for powerplants in our RACE facility; and, g) The ability to design a power plant fully 'in silico' in lieu of empirical demonstration - a growing advanced computing programme will allow us to exploit the benefits of exascale computing to bridge the gap from today's physics to tomorrows powerplants

Fusion is the process that powers the Sun, and if it can be reproduced here on Earth it would solve one of the biggest challenges facing humanity - plentiful, safe, sustainable power to the grid. For fusion to occur requires the deuterium and tritium (DT) mix of fuels to be heated to ten times the temperature at the centre of the Sun, and confined for sufficient time at sufficient density. The fuel is then in the plasma state - a form of ionised gas. Our CDT explores two approaches to creating the fusion conditions in the plasma: (1) magnetic confinement fusion which holds the fuel by magnetic fields at relatively low density for relatively long times in a chamber called a tokamak, and (2) inertial confinement fusion which holds the fuel for a very short time related to the plasma inertia but at huge densities which are achieved by powerful lasers focused onto a solid DT pellet. A main driver for our CDT is the people that are required as we approach the final stages towards the commercialisation of fusion energy. This requires high calibre researchers to be internationally competitive and win time on the new generation of fusion facilities such as the 15Bn Euro ITER international tokamak under construction in the South of France, and the range of new high power laser facilities across Europe and beyond (e.g. NIF in the US). ITER, for example, will produce ten times more fusion power than that used to heat the plasma to fusion conditions, to answer the final physics questions and most technology questions to enable the design of the first demonstration reactors. Fusion integrates many research areas. Our CDT trains across plasma physics and materials strands, giving students depth of knowledge in their chosen strand, but also breadth across both to instil an understanding of how the two are closely coupled in a fusion device. Training in advanced instrumentation and microscopy is required to understand how materials and plasmas behave (and interact) in the extreme fusion conditions. Advanced computing cuts across materials science and plasma physics, so high performance computing is embedded in our taught programme and several PhD research projects. Fusion requires advances in technology as well as scientific research. We focus on areas that link to our core interests of materials and plasmas, such as the negative ion sources required for the large neutral beam heating systems or the design of the divertor components to handle high heat loads. Our students have access to world-class facilities that enhance the local infrastructure of the partner universities. The Central Laser Facility and Orion laser at AWE, for example, provide an important UK capability, while LMJ, XFEL and the ELI suite of laser facilities offer opportunities for high impact research to establish track records. In materials, we have access to the National Ion Beam Centre, including Dalton Cumbria Facility; the Materials Research Facility at Culham for studying radioactive samples; the emerging capability of the Royce institute, and the Jules Horowitz reactor for neutron irradiation experiments in the near future. The JET and MAST-U tokamaks at Culham are key for plasma physics and materials science. MAST-U is returning to experiments following a £55M upgrade, while JET is preparing for record- breaking fusion experiments with DT. Overseas, we have an MoU with the Korean national fusion institute (NFRI) to collaborate on materials research and on their superconducting tokamak, KSTAR. The latter provides important experience for our students as both the JT-60SA tokamak (under construction in Japan as an EU-Japan collaboration) and ITER will have superconducting magnets, and plays to the strengths of our superconducting materials capability at Durham and Oxford. These opportunities together provide an excellent training environment and create a high impact arena with strong international visibility for our students.

The nuclear industry has some of the most extreme environments in the world, with radiation levels and other hazards frequently restricting human access to facilities. Even when human entry is possible, the risks can be significant and very low levels of productivity. To date, robotic systems have had limited impact on the nuclear industry, but it is clear that they offer considerable opportunities for improved productivity and significantly reduced human risk. The nuclear industry has a vast array of highly complex and diverse challenges that span the entire industry: decommissioning and waste management, Plant Life Extension (PLEX), Nuclear New Build (NNB), small modular reactors (SMRs) and fusion. Whilst the challenges across the nuclear industry are varied, they share many similarities that relate to the extreme conditions that are present. Vitally these similarities also translate across into other environments, such as space, oil and gas and mining, all of which, for example, have challenges associated with radiation (high energy cosmic rays in space and the presence of naturally occurring radioactive materials (NORM) in mining and oil and gas). Major hazards associated with the nuclear industry include radiation; storage media (for example water, air, vacuum); lack of utilities (such as lighting, power or communications); restricted access; unstructured environments. These hazards mean that some challenges are currently intractable in the absence of solutions that will rely on future capabilities in Robotics and Artificial Intelligence (RAI). Reliable robotic systems are not just essential for future operations in the nuclear industry, but they also offer the potential to transform the industry globally. In decommissioning, robots will be required to characterise facilities (e.g. map dose rates, generate topographical maps and identify materials), inspect vessels and infrastructure, move, manipulate, cut, sort and segregate waste and assist operations staff. To support the life extension of existing nuclear power plants, robotic systems will be required to inspect and assess the integrity and condition of equipment and facilities and might even be used to implement urgent repairs in hard to reach areas of the plant. Similar systems will be required in NNB, fusion reactors and SMRs. Furthermore, it is essential that past mistakes in the design of nuclear facilities, which makes the deployment of robotic systems highly challenging, do not perpetuate into future builds. Even newly constructed facilities such as CERN, which now has many areas that are inaccessible to humans because of high radioactive dose rates, has been designed for human, rather than robotic intervention. Another major challenge that RAIN will grapple with is the use of digital technologies within the nuclear sector. Virtual and Augmented Reality, AI and machine learning have arrived but the nuclear sector is poorly positioned to understand and use these rapidly emerging technologies. RAIN will deliver the necessary step changes in fundamental robotics science and establish the pathways to impact that will enable the creation of a research and innovation ecosystem with the capability to lead the world in nuclear robotics. While our centre of gravity is around nuclear we have a keen focus on applications and exploitation in a much wider range of challenging environments.