Fusion Power has the potential to solve one of society's greatest challenges: universal access to plentiful, safe & sustainable energy. A person's entire lifetime energy needs can be supplied from fusion energy using the deuterium taken from a domestic bath of water and the tritium that can be bred from the lithium in a single mobile phone battery. Fusion power plants cannot suffer any type of runaway and they do not produce any direct greenhouse gas emissions. However achieving fusion is technically challenging: it requires heating the deuterium & tritium fuel to millions of degrees. At this temperature, the fuel becomes a plasma - a gas of charged particles. The plasma must be confined for sufficient time at sufficient density in order to get more energy out than we put energy in. There are a number of approaches being explored but the most successful are (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 but at huge densities. The exciting news is that fusion is now entering a golden era. Since 2020, there have been substantial scientific breakthroughs, such as at JET in the UK and at NIF in the US. There has been dramatic expansion into the private sector with over 30 companies globally pursuing a range of approaches and many more establishing the fusion supply chain; governments around the world, but especially in the UK, are investing to accelerate fusion delivery. A remaining critical barrier to making fusion a reality is the shortage of people who understand the inter-related operational constraints for both the plasma fuel and its containment materials, including the breeding of tritium from lithium, all of which must be satisfied simultaneously. The EPSRC CDT in Fusion Power will build on our existing success and international reputation to become the global beacon for training the next generation of fusion leaders. At the core of our CDT is the partnership between six leading research-intensive universities and more than 20 private companies, UK & international labs and government agencies. Our students will benefit from a systems-thinking-based technical training in plasma physics and materials science including tritium breeding & handling. They will benefit from training delivered by non-academic partners in topics such as regulation & licensing, commercialisation & entrepreneurship, sustainability, financing & investment and project management. Through the CDT partners, the students will use internationally leading experimental facilities and high performance supercomputers. Initially through their supervisors and then increasingly independently, students will access international networks of institutions and fusion professionals. During their PhD, students will have the opportunity to build their track record through presenting work at conferences and leading their own "collaboratory" mini project. These scientists and engineers will go on to solve the technical cross-disciplinary challenges, moving fusion forward faster at a rate of more than 20 scientists & engineers per year. We will increase diversity in the fusion community through: positive recruitment & admissions practices; supportive, cohort-based training activities; undergraduate fusion internships for students from under-represented groups; outreach to the public and via sustained relationships with target schools. This supply of the best people will energise the UK fusion industry and enable a global ambition for fusion power plant innovation & development.

We have long known that the nominally anhydrous mantle minerals, such as can take substantial amounts of water into them (eg 3% for wadsleyite and ringwoodite). We also know that water has a drastic effect on the physical and chemical properties of these minerals, changing phase relations by hundreds of Kelvin and causing order-of-magnitude variations in viscosity, electrical conductivity and vacancy populations. This has created a whole genre of speculation about the water content in the mantle and its effects on mantle dynamics (eg; 'The mid-mantle water filter'; Bercovici and Karato 2003: 'Nine oceans of water in the transition zone'; Smyth et al 1994: 'No water in the transition zone'; Green at al 2010). We have, however, no firm understanding of the water content of the mantle deeper than about 100 km and these papers will remain speculative until we place firm constraints on the water content of the deep mantle. We can do this by combining geophysical inversions for electrical conductivity of the geomagnetic response function with laboratory measurements of the effect of water content on electrical conductivity. This is what the current project will do using cutting-edge designer-diamond anvil cell conductivity measurements with simultaneous infra-red measurements of water content. These new data will be used in Monte Carlo simulations of the geomagnetic response function which invert directly for water content.

X-ray free-electron lasers (XFELs) are the most brilliant sources of x-rays on Earth. The highly coherent, near-monochromatic, sub-picosecond bursts of radiation they deliver make them the ultimate 'high-speed camera', capable of capturing extremely fast, atomic-level phenomena as they unfold in unprecedented detail. XFELs are therefore ideally suited to probing matter undergoing laser-based dynamic compression, whereby one or more high-power optical lasers rapidly vaporise the surface of a solid target, launching into it a compression wave that generates internal stresses many millions of times greater than atmospheric pressure. During the few billionths of a second for which they survive before being disintegrated, these targets reach extreme pressures of the kind ordinarily encountered only in planetary interiors, and experience rates of deformation rivalling those of meteoric impact events. By illuminating these short-lived samples with extremely bright XFEL pulses, we can generate x-ray diffraction or absorption spectra rich with information about their atomic arrangement, structure, and dynamics in the moments before their destruction. This ability to diagnose the dynamic response of matter under extraordinary thermodynamic conditions is transforming experimental high-pressure physics, allowing us to better understand not only the internal structure, formation, and collision dynamics of planetary bodies, but how to synthesise and recover exotic high-pressure phases of matter, and how engineering alloys and ceramics respond to the huge dynamic stresses created by hypervelocity impacts. In this project, we aim to leverage the diagnostic power of the recently commissioned European XFEL (EuXFEL), an international XFEL facility backed by a consortium of twelve countries to which the UK has committed approximately £30M in capital to date. We will exploit the EuXFEL to shed new light on the plasticity and strength of model metals dynamically deforming at extreme pressures and strain rates. Our aim is to take the 'ordinary' physical processes controlling plastic deformation that materials scientists have studied for over a century, and to examine them under the 'extraordinary' thermodynamic conditions accessible via dynamic compression. Using the UK-built, high-repetition-rate, £8M DiPOLE-100 laser recently installed at EuXFEL, we will laser-compress a range of metals and alloys to planetary pressures over nanosecond timescales at an unprecedented shot rate. We will use femtosecond x-ray diffraction to measure the ultrafast rotation experienced by our samples' microstructure, and use it to identify the plasticity mechanisms that relieve the colossal shear stresses accumulated during compression. From these same diffraction measurements, we will extract the strain state of our metallic samples, allowing us to measure their dynamic strength at extreme strain rates. We will also use EuXFEL to study these samples' x-ray absorption properties under extreme loading, with which we can track their temperature dynamics in situ. Together, these XFEL-enabled experimental measurements of plasticity mechanisms, strength, and temperature evolution have the potential to transform our understanding of material deformation physics under extreme loading conditions.

Replicating a human organ is a highly complex challenge both structurally and functionally. At the core of this grand challenge lies the critical need for vascularisation and more broadly the need for cellularisation. Cellular systems in our bodies are naturally programmed in a bottom-up fashion where structure is an evolutionary consequence of function. For instance, the need for optimal exchange and transport drives morphogenesis, manifesting itself via dynamic signalling and secretion patterns during vascularisation, alveolarization and the formation of all self-organised tissue compartments. Tissue engineers have attempted the inverse hoping function will also follow form, with a laser focus on the structure problem: the ability to produce acellular architectures such as perfusable networks for transport and microporous scaffolds for cellular aggregation. These top-down engineered matrices are intricate yet static and non-responsive, leaving us with rudimental means of bulk seeding, cellularisation and stimulation, and limiting cell-mediated bottom-up growth and remodelling. Organotypic growth patterns are a dynamic response to physiological needs, driven by the spatiotemporally controlled release of biochemical factors and stimuli, and require extremely soft and degradable cell encapsulated extracellular microenvironments capable of bottom-up remodelling, both of which are currently only afforded at small microfluidic footprints. The 3D SPARK project offers a game-changing solution to large-scale volumetric tissue production via computed axial lithography (CAL) and computed axial stimulation (CAS) - the optical inverses of computed axial tomography (CAT). Volumetric processing challenges conventional wisdom in tissue engineering showing that complex and delicate 3D cellular architectures can be produced all-at-once without relying on slow, sequential processing of biological matter, and that large volumes of manufactured tissue can be accessible at a single cell level without a need for physical manipulation or slow optical scanning. At its core, this revolutionary CAT-inspired method utilises a superposition of 2D angular light projections to construct a 3D spatial distribution of exposure dose, and volumetrically trigger photopolymerization (bioprinting), photorelease (biomodulation) and photoexcitation (imaging) to regulate and monitor key cellular events during tissue development in a photoactive cell-encapsulated hydrogel matrix. With light-mediated volumetric processing and the ability to pattern light intensity in 3D at multiple wavelengths, we introduce a scalable solution to: (1) trigger photopolymerization and manufacture intact vascular structures in such soft (<10 kPa) cell-encapsulated photoactive gels; (2) control the light-induced depletion of chemical species such as oxygen (via radical quenching), and secretion of biochemical factors such as growth factors (via uncaging) directing tissue development across the entire volume; and (3) rapidly image the entire volume to monitor 3D cellularisation concurrent with photomodulation and tissue growth. In our tissue models, larger features such as macrovascular networks are designed and volumetrically printed in a top-down fashion and are internally coated with endothelial cells (ECs). Finer features such as microvascular capillaries are then stimulated with light to emerge and develop from sparsely encapsulated ECs within the printed gel to bridge the macrovascular gaps in a bottom-up fashion. This all-in-one platform goes beyond patterning the physical and chemical properties of the matrix, to enable dynamic manipulation of cellular processes allowing us to accommodate for top-down engineering and bottom-up development simultaneously. Hence, the proposed technology will be the dream tool of tissue engineers giving them spatiotemporal access to large volumes of printed tissue at a single cell level with light in a way never achievable before.

Thermonuclear fusion is the mechanism by which energy is generated in the Sun. For decades scientists have been attempting to harness fusion for electrical power production because of the huge advantages it offers as a safe, clean and almost inexhaustible supply of energy. In laboratory experiments, fusion is normally studied by heating the heavy isotopes of hydrogen to very high temperatures forming a plasma, in which the rapid motion of the positively charged ions is sufficient to overcome their electrostatic repulsion and allow them to undergo nuclear reactions. One of the main approaches to extracting energy from these reactions is Inertial Confinement Fusion. This involves assembly of the thermonuclear fuel to ultra-high density (over 1000 times the density of water) inside a mm-scale capsule through a spherical implosion driven by high-power lasers. Central to this method is the process of ignition in which the energetic alpha particles emerging from the reactions are themselves used to further heat the fuel, resulting in a self-sustaining burn wave which releases copious amounts of energy. This is a very exciting time for fusion research because with the completion of the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL), the first laboratory facility with the capacity to demonstrate ignition is now operational. Early results from the NIF however have highlighted differences between the predictions of computer models and the behaviour observed. Most importantly the number of nuclear reactions has remained too low to initiate ignition. The PI and Co-I on this grant have worked extensively with scientists at LLNL to understand the origins of these discrepancies and participated in the Science of Ignition workshop which identified priority research directions to address these issues. For this proposal we wish to capitalise upon our experience with plasmas of extremely high density and temperature to address key uncertainties in the design of inertial confinement fusion experiments and the physics of ignition and work to provide an explanation of why the current design does not achieve ignition and burn. Key areas of research will include understanding the way in which the radiation used to drive the implosion is absorbed in the surface of the capsule, the susceptibility of the imploding capsule to hydrodynamic instabilities which cause the fuel to disintegrate before it is fully compressed and the tendency of the high temperature and low temperature regions of the fuel to stir and mix together which quenches the burn. We will also investigate the physics of the ignition process itself, evaluating whether the energetic alpha particles are able to escape the fuel before depositing their energy and the role of spontaneously generated magnetic fields which provide a form of thermal insulation and serve to keep the heat within the fuel. Part of the work will involve developing a number of advanced computer modelling capabilities. In addition to their use in fusion research, these capabilities can also be used to exploit large scale laser facilities for fundamental research in plasma physics, nuclear physics and laboratory astrophysics. Using these computer models to simulate a fusion capsule in which we deliberately introduce an imperfection, we can calculate what characteristic signatures of this defect are embedded within the flux of energetic neutrons and X-rays emanating from the reacting fuel. Comparing synthetic diagnostic data with that obtained in experiment then allows us to isolate which physical processes are responsible for limiting fusion performance. The same computer models can then be used to design improvements which mitigate these effects and allow us to make progress towards achieving ignition. The work described in this proposal therefore represents an opportunity for UK science to make a significant contribution to what would be a major scientific achievement.