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μ15 High energy microfocus beamline

Prepared for Diamond SAC/DISCo November 2020

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1. Acknowledgements

This proposal was produced under the direction of the μ15 User Working Group (UWG): Prof Andrew Beale University College London Dr John Claridge University of Liverpool Prof Serena Corr The University of Sheffield Prof Andrew Goodwin (Lead external champion) University of Oxford AssProf Kirsten Marie Ørnsbjerg Jensen University of Copenhagen Dr Enrique Jimenez-Melero (DUC representative) University of Manchester Dr Raymond Osborn Argonne National Laboratory Dr Arkadiy Simonov ETZ Zurich Dr Helen Blade of AstraZeneca kindly read and commented on sections of the draft proposal.

The UWG met via videoconferencing on the following dates to plan and discuss this proposal: 1st UWG Meeting: 14:00-16:00 (BST) 18/09/2020 2nd UWG Meeting: 14:00-16:00 (BST) 12/10/2020 In addition, the UWG and Diamond staff were in regular email contact during the preparation of this proposal.

A Community Engagement Webinar took place on 10:00-11:30 (BST) 02/11/2020 with the following agenda: Introduction to Diamond-II and the Crystallography Science Group vision, Dr Joe Hriljac μ15 Specification and Techniques, Dr Philip Chater μ15 Science Opportunities, Prof Andrew Goodwin Q&A Session We thank the large number of attendees (peak of 100 participants, which was the maximum possible under the videoconferencing license), and in particular those who contributed questions and gave offers of support which helped shape this proposal.

The compilation of this document was led by: Dr Joe Hriljac (Diamond lead), Crystallography Science Group Leader Dr Philip Chater, Principal Beamline Scientist I15-1 We acknowledge the following Diamond staff for their contributions to this proposal: Dr Maria Diaz Lopez, Beamline Scientist I15-1 Miss Rachel (Wai Chi) Tang, PhD student (Diamond and University of Birmingham) Dr Christine Beavers, Principal Beamline Scientist I15 Dr Kawal Sawhney, Head of Optics & Metrology Dr John Sutter, Senior Optics Scientist Dr Lucia Alianelli, Senior Optics Scientist Dr Dean Keeble, Data Analysis Scientist Dr Elizabeth Shotton, Head of Industrial Liaison Group

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2. Executive Summary

In the century since the dawn of crystallography, the field of structural science has exploded from studies of simple mono-phase ordered crystal systems to include disordered, nano-structured, multi-phase and non-crystalline materials. μ15’s objective is to not only understand these increasingly complex materials, but also the increasingly complex devices in which they are used. μ15 will deliver this by revealing how bulk materials change at the atomic level, using crystallographic and local structure analyses, and how they interact at the micron level, using multi-dimensional mapping. By enabling more studies of real devices under operating conditions, μ15 will revolutionise our understanding of crucial devices like batteries, biological implants or catalyst monoliths.

μ15 will deliver a suite of crystallographic techniques with the potential for high impact in a wide range of scientific fields. In this proposal we provide science cases for how μ15 can contribute to all five major physical science challenge areas highlighted in the Diamond-II Advancing Science case document, as well as a sixth area which overlaps with the life science challenges. The ability to study complex materials, heterogeneous systems and real devices means μ15 is perfectly positioned to deliver impact across a wide range of technology readiness levels. In recognition of this far-reaching applicability we have gathered huge support from a wide range of interested users from academia and industry which represents a small fraction of the potential user community.

These advanced crystallographic techniques require high energy X-rays (35-100 keV) delivered into a highly stable microfocus beam. The best way to deliver these capabilities on Diamond-II is to relocate the majority of high-pressure work to a dedicated nanofocus undulator beamline, NExCUBe, allowing I15 to undergo a complete upgrade to μ15. The synergistic development of beamline hardware and software will allow for automated collection, processing and analysis of data, enabling real-time experiments.

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3. Scientific case

3.1 Introduction μ15 will provide a range of new and enhanced tools for the high- crystallography community (Figure 1), allowing advanced resolution measurements to become routine and facilitating increasingly depth- computed complex experiments to inform some of the greatest scientific resolved tomography challenges of the modern age. This will be delivered through the XRD synergistic development of hardware and software targeting processed and, in many cases, analysed data in as close to real- SXD PDF time as possible, allowing interactive steering of experiments. diffuse anomalous scattering scattering Operando powder X-ray diffraction (XRD) at high (35-100 keV) grazing energy has the penetration depths needed to probe deep within 3D-ΔPDF incidence complex sample environments and real devices. Energy scanning will enable anomalous scattering experiments for a range of high- Figure 1. Techniques available on µ15, Z elements. Multiple detectors will allow experiments optimised with strong links between techniques for speed or resolution. A multi-analyser crystal array coupled to highlighted in red. 2D detectors will allow depth-resolved studies of buried interfaces. High energies enable pair distribution function (PDF) studies which provide local structure information on crystalline, nanocrystalline, defective, amorphous and liquid samples.1 PDF can be used to understand materials in which structural fluctuations play a vital role in their functionality, including advanced functional materials displaying orbital frustration, charge density waves, metal-insulator transitions and superconductivity.2,3 A 1 μm vertically focussed beam allows studies of the local structure of thin-films using grazing-incidence PDF; these could revolutionise understanding of amorphous coatings and thin-film optoelectronics.4,5 X-ray diffraction computed tomography (XRD-CT) will provide spatially-resolved information inside representative 3D volumes of bulk polycrystalline samples, revealing very fine structures after manufacture and complex spatio-temporal interactions as a response to external stimuli during service.6 Unlike standard X-ray CT, which provides simple contrast imaging based on X-ray absorption, XRD-CT allows the mapping of physico-chemical composition and (evolving) behaviour of functional materials, often as they perform their function (recently termed ‘5D imaging’).7 This insight informs the understanding of the chemistry behind phenomena that by accident or design are heterogeneous and therefore allows for the design of better performing materials with enhanced predictions of service behaviour and lifetime. μ15 will offer the ability to routinely make use of these powerful data collection and processing methods. Extending these studies to include PDF-CT measurements will provide a complete physico-chemically resolved description of crystalline and amorphous components within devices. μ15 will also perform high energy single crystal X-ray diffraction (SXD) studies to exploit diffuse scattering to probe deviations from perfect periodicity caused by point defects, extended short-range order, or thermally induced lattice vibrations. Traditionally, such measurements have been interpreted by performing atomistic simulations of the disorder, which can be slow and may not generate unique structural solutions. The latest generation of fast area detectors allows measurement of sufficiently large contiguous scattering volumes that data can be reliably transformed to generate real space probability maps of interatomic vectors. The 3D-ΔPDF is calculated by eliminating Bragg peaks before calculating the transform, so only contains vectors that deviate from the average crystal structure. Although this is another representation of the same data, it is much more intuitive to interpret without the need for extensive modelling and provides robust information on, e.g., the correlation lengths of short-range order. This makes it possible for the speed of experimental interpretation to keep pace with increasingly rapid data acquisition as well as making the results more amenable to advanced analysis methods such as machine learning. 4

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3.2 Science enabled by project 3.2.1 Energy materials Can we observe how ions move within materials? Optimizing the performance of energy storage materials at a more fundamental level requires an understanding of the factors that limit ionic mobility in both the bulk of battery electrodes or solid-state electrolytes and across their interfaces. There have been significant advances in our ability to simulate ionic transport with ab initio theory, leading to vast materials genome libraries of candidate materials. However, our ability to validate such calculations has been hindered by limitations in our ability to measure ionic correlations in situ as a function of concentration. This has begun to change with recent advances in X-ray scattering analysis, and μ15 will enable these advances to be applied under operando conditions in increasingly complex materials. 3D-ΔPDF methods allow ionic correlations to be probed in all three dimensions of a crystalline lattice, on length scales that vary from 1 to 50 nm, covering the range from nearest-neighbour interactions to quasi-long-range order.8 Order-disorder phenomena are known to hinder ionic mobility, but can in principle be mitigated by, for example, co-doping with aliovalent cations.9 With μ15 it will be possible to assess the effectiveness of such materials science strategies to assist in the design of the new materials. How can we understand what is happening inside real batteries while they are operating? Unpicking the transformations occurring inside electrochemical devices such as batteries and fuel cells will be key to predicting materials with enhanced performance, improved longevity and reduced cost. Devices for energy storage and conversion are complex, multi-component systems which pose a significant characterisation challenge. Non-destructive probes capable of operando studies are therefore needed which can resolve not just the elemental, but also the crystallographic distributions within these devices. XRD-CT has proven powerful for identifying variances in battery electrode composition at the single grain level, enabling the rationalisation of deactivation mechanisms.10,11 The 3D maps of diffraction data allow devices to be explored in extraordinary crystallographic detail; from the quantification of phases present to their atomic structural parameters (Figure 2).12 Such studies are very powerful not least because the combination of bright high energy X-ray sources coupled with high performance detectors allows for the imaging of real devices profiled under more realistic operational conditions (e.g. real AAA type batteries during charge and discharge). This mitigates the challenges and risks when trying to correlate lab measurements with the Figure 2. Evolution of the Li performance in the field. Micron-scale mapping will allow the study of composition variation within a interfaces and their evolution with aging in the next generation of all- 12 battery during charging. solid batteries.13

Commercially-applied layered transition metal oxides LiNixMnyCozO2 continue to present fundamental challenges for studying structural disorder through Ni/Li site exchange.14 In addition, amorphous and highly disordered functional materials are gaining interest in many energy technologies,15–19 including the emerging class of disordered rock salt cathodes which display high initial capacities but suffer from capacity fade with cycling.20 In-depth local structural analyses with repeated cycling are required to understand the role of disorder in electrochemical behaviour and to test stabilisation strategies. Extending XRD- and PDF- CT21 methods to operando battery and fuel cell studies on the sustainable energy technologies of the future utilising disordered functional materials will provide unique insights into how complex systems evolve over different length-scales during operation where polycrystalline, nanostructured, and amorphous materials coexist and transform.22–24 5

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3.2.2 Chemistry and catalysis What is the real active form of the latest catalysts while they are working? Nanostructured and amorphous oxide materials are being intensively studied for use as catalysts. For example, nanostructured cobalt and iron-based oxides, sulfides and phosphides,25–28 as well as iridium oxides29 are promising electrocatalysts for water splitting reactions. The development of such nanostructured amorphous catalysts relies not only on the ability to characterise the structure/property relations in materials with no long-range atomic order, but to do this under the working conditions of the catalyst and any support material. There is currently very little knowledge on how the local structure of such electrocatalysts change during catalysis, although such structural changes may be large and can heavily affect catalyst function.30 Rapid operando spatial mapping measurements of local structure using PDF-CT will completely change the way we can study real Figure 3. Crystallographic data extracted catalyst materials and go beyond the model systems currently from 3D reconstructions of XRD-CT data investigated. Recent demonstrator studies have shown that collected on a catalysis bed. a) Weight profiling of catalytic materials with XRD-CT has proven powerful for percent, b) crystallite size (nm) and c) 7 identifying the formation and distribution of active species during lattice parameter (Å). both the catalyst activation phase and under reaction conditions (Figure 3).7 These studies typically use a beam size of 1-100 μm to explore sample inhomogeneities. Extending these studies to routinely include total scattering and PDF-CT data will give access to details of both crystalline and amorphous components and extract chemically-, spatially- and temporally-resolved data, permitting 5D imaging of real systems. Together XRD-CT and PDF-CT have proven powerful for providing a more comprehensive assessment of nanoparticle behaviour when a range of particle sizes are present.31 Studies on large-scale devices will allow researchers to understand issues such as gradients in catalytic reactor beds and ultimately understand monoliths in emission control catalysts. With rapid data acquisition it may even be possible to employ rapid gas switching and to perform spatially resolved modulation excitation experiments to even identify the active species with spatial distribution – a truly unique proposition for functional materials characterisation. How do solid-state structures form? One of the largest knowledge gaps in chemistry is an atomistic understanding of the nucleation process of solid-state from solution.32 Classical and non-classical nucleation theory is currently used to describe material formation, but neither theory describes nucleation on an atomistic level. In recent years, the existence of ‘prenucleation clusters’ has been discussed. The atomic structure of such clusters, and the relation between their structure and the crystalline material forming, remains unknown. Atomic scale information on these mechanisms is needed to develop computational methods for synthesis prediction, which could revolutionise solid-state synthesis in a similar way to fragment screening in pharmaceutical development.33,34 Many in situ experiments have been developed to study these processes using electrons, neutrons and X-rays. In situ studies using PDF analysis have provided atomic structural information on ionic clusters in solution, intermediate and prenucleation cluster structures, making it possible to follow structural rearrangements taking place during chemical synthesis.35 The next step is to expand these in situ studies to look at increasingly complex synthetic methods, such as hydrothermal-, microwave- and electro- syntheses. For example, engineered heterogeneity in metal-organic frameworks formed through rapid electrosynthesis has introduced defects with high catalytic activity36; exploration of how these defects form on the synthesis timescales using μ15 will provide a significant step towards understanding the role of prenucleation clusters in synthesis. 6

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3.2.3 Advanced materials and quantum materials How do we move beyond the CMOS technology? Most electronics rely on complementary metal-oxide-semiconductor (CMOS) transistors. While the rapid decrease in size of these transistors has seen components shrink to less than 10 nm, the switching mechanism has remained largely unchanged. A completely new generation of switching devices are required to reduce switching energy, lower switching voltage and enhance logic density. A potential structure of such a device utilising advanced quantum materials has recently been proposed,37 but this requires room-temperature multiferroics with improved magnetoelectric coupling beyond what the archetypal BiFeO3 can offer. 3D-ΔPDF allows for the local structure to be resolved in three dimensions, vastly increasing its sensitivity to small deviations compared to standard PDF methods.38 A small number of 3D-ΔPDF studies using X-rays and neutrons are already starting to provide valuable insights into a range of materials and phenomena, such as the thermoelectric material PbTe39 or phase-change materials like Ge4Bi2Te7 which is under consideration for data storage applications.40 Recent software advances41 have allowed the 3D-ΔPDF data to be refined in order to fully determine quantify these deviations from the average structure (Figure 4). μ15 will bring these studies to a much wider user community, and also allow correlation of electronic properties with minute structural deviations under a wider range of Figure 4. Observed, refined and external stimuli, such as temperature, electric field and electric charge. difference 3D-ΔPDF from PbTe A complete understanding of how the local structure responds to showing a pattern of local dipole external stimuli could lead to a new generation of multiferroic formation extending for several unit cells at 125 K.39 materials and components. How do we understand the structural response to emergent phases in quantum materials? In order to overcome fundamental limits to the performance of conventional silicon-based electronics, there is a need to identify new materials that will underpin the future of quantum computing and low- power electronics. Much attention is focussed on quantum materials that exhibit novel correlated electron phases, often generated by strong spin-orbit coupling. These materials exhibit properties such as topologically protected transport or non-Abelian quasiparticles that are required to enable new technological approaches. Structural studies are important in characterizing these emergent electronic phases, since lattice degrees of freedom often play a role in stabilizing them. Nevertheless, the associated distortions can be very weak or short-ranged. For example, vanadium dimerization at the metal-insulator transition in pure VO2 induces a first-order structural phase transition.42 However, with molybdenum doping, the structural response to the electronic transition becomes short-range. 3D-ΔPDF measurements show that the vanadium dimers are only correlated in two dimensions over a 43 length scale of ~50 Å (Figure 5). Similarly, the failure to observe Figure 5. Diffuse scattering and 3D- structural order in Sr3Ir2O7, in spite of spectroscopic evidence of a ΔPDF data below the metal- density-wave instability, has been attributed to a short-range insulator transition in V1−xMoxO2, response.44 It is important therefore to be able to go beyond showing the transition from 3D conventional crystallography and monitor the structural response to order to frustrated 2D order at 43 electronic correlations over a range of length scales, from a few to a composition x = 0.19. few hundred Angstroms, which µ15 is designed to accomplish.

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3.2.4 Earth, environment and heritage How will the UK safely clean up and store its legacy nuclear waste? The clean-up of the UK’s nuclear sites and legacy waste is the largest, most important environmental restoration programme in Europe.45 Achieving passive safety for the radioactive materials produced during decommissioning is paramount for their long term storage in a Geological Disposal Facility (GDF). Most GDFs include a backfill material to surround the storage containers that can act as a thermal and mechanical buffer and also to remove any radionuclides that escape from the primary containment. Montmorillonite clay (MMT) is the best backfill candidate identified to date. MMT has recently been studied using X-ray CT and XRD to investigate the 3D microstructure of compacted samples.46 The study identified the presence of a gel phase within the pores and differences in grain sizes of clay particles before and after ion exchange with Cs. What is missing from this study is an in situ investigation of the transformation of the starting Na- MMT into the saturated Cs-MMT in the actual compacted material with detailed knowledge of the degree of uniformity as a function of position. This would best mimic a real-world scenario and would provide information needed in engineering design and in support a safety case. This could be done using XRD-CT where changes in the lattice parameters of the MMT would indicate the relative amount of Na and Cs. PDF- CT could be used to study the crystalline clay particles and also give information about the unknown pore gel phase. New primary waste containment systems are also being developed which require stringent characterisation before deployment. Basic science is key to understanding the nature and formation of complex multiphase wasteforms that incorporate radionuclides and underpin the development of robust safety cases. Potential materials for decommissioning waste include a variety of tailored cements and products of thermal treatment. The latter can be a mixture of ceramic phases such as SYNROC, purely vitreous or a glass-ceramic composite. These wasteforms are invariably produced as 3D monoliths. To date X-ray scattering studies have only been done on crushed powders or thin 2D slices which loses some or all of the spatially resolved compositional and crystallographic information from within the monolith. The use of XRD- and/or PDF-CT would vastly improve the characterisation, enabling a deeper understanding of the as-prepared assemblage. The new Active Materials Laboratory (AML) at Diamond will facilitate experiments like this and make μ15 the ideal location to perform these studies. How do we protect and learn about items of cultural heritage? Cultural heritage artefacts are often complex and heterogeneous, containing original and later (from degradation/conservation) material. Diffraction provides a non-destructive way of probing multi-scale artefacts and can provide crucial information required to determine ancient manufacturing processes, evaluate their conservation state and up underpin best conservation practice.47 Diffraction mapping has provided insights into highly varied topics including Vermeer’s discerning use of subtly different white Pb- Figure 6. Compositional maps of containing pigments in Girl with a Pearl Earring (c. 1665)48 and polyethylene glycol (PEG) and zinc blende Rembrandt’s Homer (c. 1663),49 and even to identify the painting particles determined from PDF-CT data of style of Van Gogh (Sunflowers).50 A recent study on the preserved wood from the Mary Rose.51 preservation of wood from King Henry VIII’s 1511 warship, the Mary Rose, used PDF-CT to provide position-resolved quantitative structural information about species on different length- and concentration-scales (Figure 6).51 Maps of the highly heterogeneous samples provided the composition and location of nanostructured zinc sulfide particles, precursors to potential acid attack on the wood in aerobic environments, as well as the location of polyethylene glycol used to provide mechanical stability to the wood. Non-destructive mapping using XRD- and/or PDF-CT on μ15 will dramatically improve the accessibility of this technique for non-experts and lead to new insights into a material’s history across a wide range of cultural heritage artefacts. 8

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3.2.5 Pharmaceuticals and biomaterials Can we improve pharmaceutical delivery methods? 60% of active pharmaceutical ingredients (APIs) currently under development are poorly soluble and methods to study and better understand mixed solid formulations are of significant interest. Synchrotron studies have much to offer,52 as demonstrated by recent work on pharmaceuticals for HIV treatment53 and the development of new methodology for the analysis of PDF to quantify the degree of crystalline and amorphous forms of a drug in a complex mix of solids.54 Wider application of PDF characterisation to the formation of other amorphous formulations, such as micelles, a) b) vesicles and nanocapsules, could lead to predictive formulation design. The formulation platform needs to be optimised on a case-by-case basis for efficient drug delivery. The development of predictive formulation and delivery design is necessary to accelerate and improve this process. μ15 will support this Figure 7. Reconstructed image cross-section of acceleration by providing unprecedented detail on not only the powder beds from X-ray CT analysis of (a) delivered forms, but also the impact of variables in processes α- and (b) β-polymorphs of L-glutamic acid. such as hot-melt extrusion and compression on the delivered The 3D image provides a view of the powder forms. One standard formulation platform is a tablet where the bed morphology and its variation along the API is invariably mixed with one or more other solids. Since axial coordinate.56 2004, X-ray CT has been used to produce density measurements on tablets and highlight inhomogeneities due to segregation during mixing and/or tablet formation55; at best such inhomogeneities could lead to unpredictable dissolution behaviours and at worst localised pressure differences could induce a phase change to a polymorph with different physiochemical properties. X-ray CT has continued to provide ever-improving information such as the morphology of free- flowed and gravity consolidated crystal powder beds of the α- and β-polymorphs of L-glutamic acid (Figure 7).56 Studies at μ15 could take this further by using XRD-CT and PDF-CT to give micron-scale mapping of the atomic structure from the 1 Å to 1000s Å scale, providing polymorphs and phase fractions for both crystalline and amorphous components. The ability to gain structural insights into transformations within amorphous formulations during processing using PDF-CT could open up many more APIs as potential candidates and revolutionise this field. Can we make load-bearing biomaterials that work with the body? Current biomaterial research efforts involve the development of materials that promote an appropriate host response to ultimately fully incorporate the new material in a way which is indistinguishable from the body. Additionally, the biomaterials’ mechanical properties (i.e. elasticity, strength) should match those found within the body for a seamless replacement, else this could cause further health issues. Some of the highest load-bearing components within the human body are bones and teeth. In the case of load-bearing bone, this means balancing mechanical properties with the additional requirement of taking an active part in the continuous process of growth and reabsorption. Amorphous calcium carbonate has demonstrated good biocompatibility and is able to be reabsorbed by the body,57 although mechanical properties make it unsuitable for a direct bone replacement. The next generation of biomaterial components are therefore likely to be made up of a load-bearing (crystalline) component alongside a scaffold (amorphous) material which supports and facilitates the proliferation and differentiation of new cells. Use of PDF to detect strain in dental implants containing crystalline and amorphous components has recently been demonstrated.58,59 This can be extended to other load-bearing implant materials such as bone replacements. In situ PDF-CT during stress/strain cycling will reveal how both the amorphous and crystalline materials in these biocompatible implants react to external stimuli, informing mechanical modelling of these devices and informing the next generation of implants. Effective new biomaterials will improve people’s quality of life and minimise the number of surgeries which will also reduce healthcare costs. 9

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3.2.6 Materials engineering and processing How do we design and qualify better alloys for use in low-carbon nuclear energy production? Core reactor structural materials (i.e. claddings, reactor pressure vessel steels, control rods, internals) undergo a continuous bombardment of radiation, in combination with elevated temperatures (<400°C in current fission reactors and <1000°C in future low-carbon Gen IV fission reactors and fusion systems), mechanical stresses and corrosive coolants. Bulk volumes of (active) industrial reactor materials are difficult to access, handle and test. Accelerated testing can be done using ion beams as a proxy for neutron damage,60 yielding a radiation damaged surface layer of 0.1-50 m depth and low activity. Currently, structural characterisation is mainly performed locally using transition electron microscopy (TEM) and in most cases requires focussed ion beam (FIB) sample preparation that can introduce unintended damage. Characterisation using grazing incidence PDF on μ15 could revolutionise the current understanding of these disordered surfaces.61,62 Should this be successful, ion beam campaigns could inform safety cases and accelerate future alloy designs. Moreover, small volumes of neutron irradiated (active) materials are gradually becoming available to the scientific community and are expected to expand in the next years; those small active bulk samples should be thermally and mechanically tested in situ to evaluate the lifetime impact of the service radiation environments. The 15 enhanced capabilities in terms of high penetration depths, microfocus beams and high flux, facilitated by Diamond’s new Active Materials Laboratory, would make this work possible. The results could impact nuclear safety decisions, the UK’s active involvement in the Gen IV international community and the safe deployment of fusion reactor technology. How do we improve manufacturing? Advanced manufacturing techniques such as metal injection moulding63 and additive manufacturing64 (AM) are some of the fastest growing industrial sectors. Currently 3D-printed metal product volumes remain small compared to those from standard manufacture and a limited number of well-established alloys are used. The rapid cooling rates and spatially variable temperature gradients lead to complex 3D microstructures. These microstructures are characterised by fine solidification structures, chemical segregations, residual stresses and high dislocation densities, all of which present a spatial distribution along the 3D build. The 3D printing of advanced ceramics is at a very early stage of development and adoption.65 In metals and ceramics, the reliable through-process modelling strongly needs experimental input in bulk structures during manufacture at fast collection times and spatially resolved, together with a 3D reconstruction of the bulk microstructures and chemistry, all linked to process parameters. The ultimate goal is 4D mapping of the microstructures during fast manufacture processes. Diffraction contrast tomography (DCT) has provided valuable information on the orientation of grains within a sample during processes like Figure 8. 3D reconstruction of recrystallisation (Figure 8),66 although the stringent sample requirements recrystallized grains in a volume for DCT limit its wider use.67 Wider application of XRD-CT may provide of partially recrystallized Al sample, determined using DCT.66 more opportunities to address these issues. Currently single crystal diffraction data are typically filtered out of data prior to tomographic reconstruction in order to supress artefacts from the reconstructed dataset, which will be an increasingly common issue when moving to smaller beam sizes.68 Instead of disregarding the crystallographic and orientational information that the single crystal data provides, utilising new combined XRD-CT and DCT analyses could provide transformative insights into these materials. The enhanced spatio-temporal resolution will enable detection of the early stages of grain formation during phase transformations or recrystallization and therefore validate, or otherwise, classical nucleation theories in bulk polycrystalline materials produced by innovative manufacture. 10

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3.3 Diamond-II portfolio

The redevelopment of I15 into µ15 benefits from higher flux at operating energies due to the increase in storage ring energy to 3.5 GeV and will allow operations up to 100 keV. It will be facilitated by the move of the majority of the current extreme conditions science programme on I15 to a much more suited undulator beamline NExCUBe. This will allow a rebuild of the optics and stages so they are optimised for the operando studies and techniques such as XRD-CT, PDF-CT and 3D-∆PDF that underpin much of the μ15 science case. The 10-year roadmap for the Crystallography Group at Diamond-II aims to deliver five dedicated beamlines which span a range of standard operating energies, beam sizes and capabilities (Table 1). There is synergy between µ15 and other beamlines in the group. I19, for example, will continue to do single crystal diffuse scattering studies on organic molecules, but the higher energies available at µ15 will simplify data corrections for higher-Z samples and allow more complex in situ studies. I11 will continue to provide the highest possible resolution data and the unique Long Duration Experiments facility, but µ15 will be able to provide high resolution data at higher energy for more absorbing samples and sample environments. NExCUBE will do the bulk of the extreme conditions experiments, but PDF studies in diamond anvil cells will continue on µ15. I15-1 will continue to operate as a dedicated PDF beamline for high throughput work, but its three fixed operating energies (40, 65 and 76 keV) rules out anomalous scattering techniques and its inherently asymmetric beam profile (700 (h) × 10 (v) μm2) means PDF-CT would be limited to a collimated beam size of ~100 × 100 μm2 which is insufficient spatial resolution for many science cases.

Table 1. Selected characteristics of Diamond-II Crystallography Group beamlines. Beamline Main Techniques Energy Range (keV) Beam size (h × v) NExCUBe Extreme conditions science, (sub)micron 15–40, ~300 × 300 nm2 (EH2) crystallography optimised at 30 ~30 × 30 µm2 (EH1) µ15 High energy scattering, operando studies, XRD- 35–100 ~40 × 40 µm2 (EH2) and PDF-CT, 3D-∆PDF ~10 × 1 µm2 (EH1) I11 High resolution and long duration 8–35 <2.5 × 0.7 mm2 (EH1 powder diffraction 0.4 × 0.4 mm2 (EH2)

I15-1 Capillary PDF experiments 40, 65 or 76 700 × 10–150 µm2 I19 Single crystal chemical crystallography, in situ 6–30 ~30 × 30 µm2 (EH1) single crystal studies, diffuse scattering studies ~60 × 60 µm2 (EH2)

The 3D scattering techniques that will form a large part of the µ15 portfolio are in rapid development in the international synchrotron community. At Diamond, I15 and I12 are the only high energy beamlines and are therefore the only truly viable suitable sources which can be exploited for these techniques. Developing routine microfocussing capabilities with the I15 wiggler will complement I12 which operates with much larger beams and often above 100 keV. μ15 will also be complementary to DIAD which will operate at lower energies (7-38 keV) and is designed to combine imaging (radiography and tomography) with diffraction (powder or single crystal) information in a different way. One can also envisage XRD-CT investigations in combination with I14 (Hard X-ray Nanoprobe, 5-23 keV) to look at details of single grains69 inside a small custom-built cell with μ15 mapping on the micron length-scale to look at variations in the same materials within a real device, all of which all feed into multi-length-scale modelling of the whole system. In addition to hardware development of µ15, new integrated software stacks for data collection, reduction and analysis will be developed and these will benefit operations at other beamlines, particularly I12 which will continue to undertake XRD-CT experiments albeit with lower spatial resolution but potentially at higher energies.

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3.4 Academic user community and beneficiaries µ15 will deliver techniques to support users across the disciplines of materials science and engineering, chemistry, physics and environmental sciences. Research areas include some listed in the EPSRC portfolio for funding growth (battery and fuel cell materials, dielectrics, energy storage and delivery) and to be maintained (catalysts, pharmaceuticals, superalloys, multifunctional materials, biominerals, nuclear waste remediation and storage materials), thus indicating µ15 is aligned to deliver support of UKRI objectives. XRD-CT is listed in the 2018 EPSRC X-ray CT roadmap70 as one of the “future needs” areas identified by the user community and PDF-CT is in its infancy but with huge potential as discussed in §3.2. μ15 will benefit the UK’s aim to become a world leader in battery technology for the automotive sector and support the Faraday Challenge. The capabilities of μ15 also align well with the “Atoms to Devices” theme of the Henry Royce Institute. Demand is hard to predict, but simple high energy scattering studies are already a good fraction of the I15 programme. I15-1, which shares much of the academic community, moved rapidly to an oversubscription rate of ~2 within 2 years of first light. Experience of I15-1 shows a beamline that develops techniques, integrated sample environments and suitable data processing and analysis software leads to rapid development of a vibrant community of new users. Some UWG members were chosen specifically as world leaders in XRD-/PDF-CT and 3D-∆PDF and their experience and expertise will be invaluable in guiding the development of the capabilities and to grow the user community. Academics from the relevant disciplines often have large groups of PhD students; they will often be the users who come to Diamond and their training will be important to ensure good science and also help lead to many of them continuing to use µ15 as their careers develop. Again, the successful experience of I15-1 will guide the building of the community and this will include holding workshops on the data collection, processing and analysis software that advertises capabilities and facilitates well planned experiments. Indicators of the large international community are that the 145 webinar registrants came from 45 different institutions (19 UK) in 14 different countries and statements of support came from 109 academics in 50 institutions and 14 countries. 3.5 Industrial user community and beneficiaries - impact on UK PLC The new capabilities offered by μ15 will benefit the Diamond industrial user base (including drug development, automotive, catalysis, energy, nuclear and aerospace) by enabling new insights into the behaviour of complex heterogeneous functional materials, often as they perform their function. The primary industrial aim of μ15 is therefore to grow existing engagement and attract new users within these sectors. The science case maps closely with the UK Government’s Industrial Grand Challenges such as Driving the Electric Revolution, the Faraday Battery Challenge, Low Cost Nuclear and Manufacturing and Future Materials. The emphasis on delivering processed, and in many cases analysed, data in close to real- time will give industrial users access to cutting-edge crystallographic analyses without a prohibitively large personnel commitment and with a significantly reduced experiment-to-outcome timeline. With μ15, industrial users who are typically used to applying synchrotron methods to solve low TRL fundamental problems on samples may start to address studies on increasingly complex devices; those who are already working at higher TRLs will undoubtedly also benefit from the new capabilities. Companies specialising in bridging academic and industrial research, such as the UK SME Finden Ltd., will use μ15 as an opportunity to exploit/train new data processing capabilities for large volume data screening. This will generate further academic and industrial interest including revenue generation for the facilities and for companies/researchers offering technical and analytical support. Here we choose to take the pharmaceutical industry as one example where μ15 can significantly build on the current industrial engagement. Amorphous formulations are desirable because of their higher solubility, but pose a significant characterisation problem (cf. §3.2.5). To date, industrial studies on I15-1 have been limited to characterisation of bulk powdered APIs and formulations. With μ15, industrial users will be able to use PDF-CT to study the processes that form the amorphized API delivery system, enabling optimisation of the process and acceleration of the delivery design and control of manufacturing activities. 12

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3.6 Comparison to other synchrotron facilities, current and planned μ15 is being designed to rival other leading high energy materials science/engineering beamlines around the world. It will be unique in offering the complete package of hardware and software for XRD-/PDF-CT and 3D-ΔPDF processing and analysis. Delivering a highly user-friendly beamline offering the most advanced data collection and processing routines will allow it to compete with high energy X-ray beamlines at higher energy synchrotrons. The outline specifications of μ15 are compared with other beamlines in Table 2. The premier beamline for high energy diffraction mapping is currently ID15A at ESRF. ID15A delivers X-rays of 20-250 keV into beam sizes from 0.3 μm to 8 mm. Although ID15A delivers more flux than μ15, it is detector technology rather than flux that is currently the limiting step; for many ID15A experiments the incident beam needed to be attenuated even before the ESRF-EBS upgrade. Equipping μ15 with a triggerable detector with sub-ms read-out and large dynamic range, capable of handling both single crystal and diffuse signals in a single frame, will allow to it deliver competitive collection times for XRD- and PDF- CT. μ15 will offer higher energies and smaller focussed beams for operando diffraction than similar planned beamlines at other medium-energy 4th generation synchrotrons like DanMax at MAX IV (limited to 15-35 keV) and JATOBÁ at Sirius (10-120 keV, but using a less-bright dipole source). The μ15 aim to deliver software for 3D-ΔPDF integrated on the beamline is currently unique. The most natural competition for 3D- ΔPDF on μ15 would be from the APS which is undergoing a similar upgrade in two years’ time, but a dedicated beamline similar to μ15 is not currently planned.

Table 2. Comparison of μ15 against similar leading international beamlines. Criteria μ15, Diamond-II ID15A, ESRF-EBS† ID-1, APS‡ P07, PETRA-III Energy [keV] 35-100 20–69 [40–250] 41–136 [45–116] 50-200 Bandwidth 1×10−3 3.7×10−3 [10−4–10−2] 1.3×10−3 [1×10−4] 1×10−3 Flux [ph/s] 1×1011 @80 keV 4.5×1013 @50 keV 6×1012 [2×1011] @80 7×1011 @100 keV Focus h×v [μm2] ~40 × 40 µm2 (EH2) 300 × 300 [0.3 × 0.3] 13 × 1.4 30 × 2 ~10 × 1 µm2 (EH1) †Initial values are with standard KB focussing. [] indicates range available with other optics. ‡Values with bent double-Laue mono. [] indicates with high resolution monochromator.

3.7 Combined impact of project and added value to activities on the Harwell Campus and beyond The ISIS and Diamond Crystallography Groups strongly support complementary research programmes across many areas of condensed matter science. There is likely to be strong overlap in diffuse scattering research on SXD at ISIS with studies on µ15 and there will likely be scope for joint software developments for 3D-∆PDF processing and analysis. We received strong statements of support from the head of the ISIS Crystallography Group, Stephen Hull, and the SXD instrument scientist, Matthias Gutmann. In a recent workshop on tomography at Harwell (March 2020) representatives from Diamond, ISIS and CLF reviewed the available tools and concluded that Diamond’s Savu71 platform should form the basis of shared developments in this field. The Ada Lovelace Centre offers opportunities to support such collaborative production of digital assets. The Faraday Institution at Harwell supports battery research and there is an increasing use of Diamond beamlines and the expertise of Diamond scientists in the various programs. Battery research will be a large part of the µ15 portfolio and can contribute in areas such as developing a better understanding of the chemical processes behind device ageing and failure. STFC detector development for high energy physics programmes at CERN and X-ray free electron laser sources provides the opportunity to develop new technologies that are particularly attractive for high-rate detectors which could be the best choice for µ15.

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4. Beamline performance specification and requirements

μ15 will dramatically increase Diamond-II’s technical capabilities for operando experiments. The raw flux gains delivered by the increase in ring energy are not massive (×3 at 80 keV), but the optimisation of the beamline for microfocus high energy diffraction will provide ×100 more flux than equivalent diffraction experiments at I12. This significant increase in flux can be exploited for major scientific gains: • observe faster phenomena – e.g. pre-crystallisation species; • obtain better spatial resolution – e.g. strain evolution in metallic glass at the micron scale; • explore a larger parameter space of sample conditions – e.g. optimising catalyst bed evolution under different temperature and gas composition/flow conditions. Removal of white beam capabilities (which will be retained at I12) will allow for much more stable optics resulting in the stable microfocus beam necessary for extended mapping experiments.

A new capability for grazing incidence PDF measurements will be introduced at Diamond for the first time. The provision of 3D-ΔPDF will be new, not because of the beamline hardware, but instead because of automated software workflows and user-friendly integration making it an internationally unique facility for this technique. This is also true for XRD-CT, where Diamond has already made significant progress in delivering ‘hardware scanning’, which allows rapid synchronised data collection using a fast, triggered detector while stages scan back and forth with minimal dead time. The combination of hardware scanning with advanced data collection strategies and detectors with fast read-out will allow for dataset collection times which are competitive with instruments with more flux at higher energy synchrotrons. Provision of a user-friendly interface to these techniques will cement μ15 as a world-leading facility for microfocus mapping and tomography.

4.1 Additional developments required The delivery of μ15 as a world-leading user facility for complex crystallographic analyses will depend on the provision of data collection, processing and analysis workflows to complement the beamline hardware. The µ15 UWG comprises of XRD-CT and 3D-ΔPDF experts who are well placed to monitor where the field is developing in order to meet future needs. We will work with other crystallography beamlines to develop routines for sub-micron goniometry, potentially utilising real-time analysis of diffraction data to re-align the sample during rotation in order to facilitate 3D-ΔPDF measurements in more complex sample environments. We will engage with mapping and tomography expertise within Diamond’s Controls, Scientific Computing, Data Acquisition and Scientific Software groups to deliver on what is needed. We will draw on the latest analysis methods such as metropolis matrix factorisation72 and machine learning. We will also consult with new users who are not as familiar with the techniques to ensure that the final beamline software is user friendly and fit for purpose for a large range of the science cases. Details of the processing requirements can be found in §5.5.

Alongside supporting a wide range of user-provided sample environments, μ15 will provide sample environments to achieve a wide range of temperatures and conditions. Hutches will be set up with gas and COSHH infrastructure to support a wide range of chemistry and catalysis applications.

μKB mirrors provide the best possible flux for the μ15 beamline; however, they are best suited to a single, narrow focus. Defocussing to obtain larger beam sizes can produce striations in the beam and removing them completely changes to beam direction, necessitating realignment of an experiment. An alternative to obtain a tuneable beam size to meet the demands of any experiment may be to apply high frequency piezo oscillators to the μKB mirrors, which could effectively blur the beam size on the timescales of the data collections. The development of μKB oscillators could completely remove the requirement for CRLs.

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5. Schematic outline of beamline or project

Why upgrade I15?

The I15 superconducting wiggler source has outlived its usefulness for its original remit of extreme conditions research; the field has moved on to even smaller beams which can only be delivered with an undulator, as proposed for the NExCUBe flagship beamline project. The wiggler is, however, the optimum choice for high energy advanced crystallographic techniques proposed for μ15 at Diamond-II.

XRD-/PDF-CT and 3D-ΔPDF require a high flux, high stability microfocus beam which is far beyond what the outdated I15 optics can deliver. The current I15 monochromator has poor repeatability and stability during scanning energy, making anomalous scattering measurements and rapid energy changes almost impossible. The focussing elements suffer from stability issues due to the large travel ranges needed to accommodate white beam operation. The μ15 technique requirements can only be met by a complete replacement of the I15 optics chain. The I15 sample stages will need to be replaced in order to meet the high demands of fast mapping and tomography data collections. Exploitation of the currently unused upstream endstation, EH2, for powder diffraction work will allow complex experiments to be set up downstream in EH1 while EH2 experiments are still running. New detectors are needed provide the high Q coverage and fast read-out needed for PDF-CT data collections. μ15 is therefore an upgrade project that will supersede I15 to deliver a leading-edge crystallography beamline for the study of complex materials and devices.

5.1 Source

μ15 will retain the same 3.5 T superconducting multi-pole wiggler as I15 as it is the only way of achieving the high energies needed (>40 keV) for operando and local structure studies on the Diamond-II ring. An obsolete cryocooler system will be replaced, allowing for quicker repairs and common spares with the I12 wiggler. The increase in ring energy to 3.5 GeV will push the wiggler spectrum to higher energies, giving more flux at higher energies. I15 is capable of operating with white beam at low wiggler fields (up to 1.5 T). The white beam capability is very rarely used and requires most beamline optical components have active cooling and a large travel range, both of which are necessary for them to be used in white beam or mono beam positions; µ15 will remove the white beam capability (it will be retained at Diamond on I12) which will greatly simplify the beamline optics and allow for the high stability required to obtain reliable and constant microfocus.

5.2 Optics

The layout of the main μ15 optics is given in Figure 9. A new double crystal monochromator in Bragg geometry will be optimised to provide an energy range of 35-100 keV. Active positional feedback will provide the stable beam position necessary for micro-focussing. Smooth energy scanning capabilities will allow for anomalous scattering experiments and fast, reliable energy changes will allow multi-energy experiments which require selection between high reciprocal-space resolution (lower energy) or real-space resolution (high energy). A new large Kirkpatrick-Baez (KB) bimorph mirror pair will provide the primary vertical and horizontal focussing. Bimorph focussing will allow variable focal sizes at the sample position with fast switching, which is necessary to allow mapping of samples on multiple length scales (e.g. rough mapping with 250 μm beam size followed by fine scan over an area of interest at 40 μm beam size). The mirrors will be positioned as far upstream as possible in order to maximise the captured flux. Pd coatings will provide harmonic rejection and maximise reflectivity at high energy.

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Figure 9. Outline of the major optical components of μ15. Locations and sizes are not to scale. Two secondary focussing elements will be available to achieve microfocus, which can be selected depending on the needs of the experiment. The principal microfocus optic will be a microfocus Kirkpatrick-Baez (μKB) mirror pair capable of delivering a 1 (v) × 10 (h) μm2 beam size. These will be polished and optimised for a single fixed focus distance, and ways of delivering a range of sizes will be explored (§4.1). Pd coatings will again be applied to maximise reflectivity at high energy. The working distance will be 300 mm to enable substantial sample environments and operando setups to be placed at the sample position. The ancillary microfocus optic will be a series of Al compound refractive lenses (CRLs) mounted inside a transfocator to allow selection of different beam sizes. The CRLs provide maximum flexibility to select the beam size needed without changing the incoming beam direction. This makes them the ideal choice for mapping on multiple length-scales, but at the expense of flux compared to the preferred μKBs. 5.3 Endstations Two endstations will allow for a wide range of experiments to be performed. EH2 will allow focussing down to 40 μm and will be optimised for powder diffraction work. A primary detector will be a large, fast area detector for Bragg and PDF studies. The area detector will have a high-Z sensor (CdTe or CdZnTe) for efficiency at high energies, a pixel size of ~100 μm and integrating read-out technology. A fast stage with x,y,z,φ motion will be used for mapping and tomographic collections. When not in use, the mapping stage will hold a set of slits which will act as the virtual source for the downstream hutch, EH1. The secondary detector will be a series of multi-analyser crystals coupled to 2D sensors (2D-MAC) which will be mounted on a 2θ goniometer and based on a principle demonstrated recently73 for high resolution and depth-graded studies. EH1 will offer the smallest beams for diffraction mapping (including XRD-/PDF-CT), single crystal (including 3D-ΔPDF) and grazing incidence PDF experiments. The larger EH1 hutch will house large and small mapping stages, each with x,y,z,φ motion for tomographic collections. The smaller mapping stage can be removed and replaced with a 3-circle goniometer for single crystal work. A primary detector will again be a large, fast area detector positioned from 0.2 to 3.8 m from the sample. Ideally this detector would have a homogenous sensor (without airgaps between modules), which would allow for full single crystal data collection coverage without needing to re-scan the sample multiple times at different angles and faster PDF data collection.

Figure 10. Proposed layout of μ15 (red), I15-1 (blue) and shared rooms (yellow). X-ray hutches (OH1, OH1A, EH1, EH2 and EH3) are shown as dark colours and other rooms are shown as light colours.

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5.4 Sample preparation facilities The offline sample preparation facilities will be redeveloped to provide a suitable laboratory for chemistry experiments, along with equivalent gas handling and COSHH extraction available in the endstations so that experiments can be fully set up and tested offline. The μ15 control room will be relocated to provide better access to EH1 and EH2, freeing up space for a dedicated data analysis room (Figure 10). 5.5 Computing infrastructure and support μ15 will provide techniques with high computational demands all the way from the initial data acquisition rates through to the data processing and visualisation. Data acquisition rates of around 5 TB/hr are expected for some techniques. Acquisition will need to make use of the latest file formats (HDF5) in order to handle large datasets and high data rates. The network architecture and file structure will need to be optimised together in order to optimise detector performance. Recent developments like distributing and recombining data streams are likely to be necessary, as has been achieved previously at Diamond.74 A considerable effort will be required to ensure that data reduction is completed at the same rate as data collection. The aim will be to deliver processed data in as-close-to-real-time as possible. Data processing workflows for two computationally expensive techniques are illustrated in Figure 11. For XRD-CT (Figure 11a), the pre-process stage (corrections and integration) can be parallelised and results in a much smaller dataset for computed tomography reconstruction. It is likely that incredibly robust data screening and processing methods will need to be developed so that the massive raw datasets do not need to be stored in perpetuity. We will build upon Diamond’s Savu71 framework for tomographic data processing to better cope with complex data collection routines and to give better automation and optimisation of tomographic reconstructions with minimal user interaction. Analysis of the individual voxel datasets will be distributed to commonly available software for Rietveld analysis, such as GSAS-II or TOPAS, before recombination of the refinement results back into 3D maps for user interrogation. Cluster analysis and machine learning tools will need to be developed to highlight areas of interest within the large datasets.

Figure 11. Outline processing pipelines for a) CT-XRD and b) 3D-ΔPDF. Some of the existing processing technologies are identified. New analysis methods for 3D-ΔPDF will be developed by Diamond in collaboration with world-leaders. For 3D-ΔPDF processing (Figure 11b), the majority of the required software tools are already available from in-house (DIALS75) and third-party (Meerkat76, cctw77) developments. The challenges will be processing data in real-time and presenting clear results to users, allowing rapid feedback on the experiment. Machine learning has shown promise in identifying correlations in these large datasets78 and we will use in-house expertise to build on such developments. Better ways of visualising the data and exploring the real-space local correlations and their relationship with the average structure will also be developed. These developments would make μ15 the first beamline offering dedicated 3D-ΔPDF experiments.

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nanofocus X-ray computed tomography and correlation with macroscopic transport properties. Appl. Clay Sci. 168, 211–222 (2019). 47. Gonzalez, V., Cotte, M., Vanmeert, F., Nolf, W. & Janssens, K. X‐ray Diffraction Mapping for Cultural Heritage Science: a Review of Experimental Configurations and Applications. Chem. – A Eur. J. 26, 1703–1719 (2020). 48. De Meyer, S. et al. Macroscopic x-ray powder diffraction imaging reveals Vermeer’s discriminating use of lead white pigments in Girl with a Pearl Earring. Sci. Adv. 5, eaax1975 (2019). 49. Price, S. W. T. et al. Unravelling the spatial dependency of the complex solid-state chemistry of Pb in a paint micro-sample from Rembrandt’s Homer using XRD-CT. Chem. Commun. 55, 1931–1934 (2019). 50. Vanmeert, F. et al. Chemical Mapping by Macroscopic X-ray Powder Diffraction (MA-XRPD) of Van Gogh’s Sunflowers : Identification of Areas with Higher Degradation Risk. Angew. Chemie Int. Ed. 57, 7418–7422 (2018). 51. Jensen, K. et al. Manuscript in preparation. (2020). 52. Byrn, S. R., Chen, X. S. & Smith, P. A. Predictive and Accelerated Formulation Design Using Synchrotron Methods. AAPS PharmSciTech 20, 1–11 (2019). 53. Terban, M. W. et al. Local Structural Effects Due to Micronization and Amorphization on an HIV Treatment Active Pharmaceutical Ingredient. Mol. Pharm. 17, 2370–2389 (2020). 54. Geddes, H. S., Blade, H., McCabe, J. F., Hughes, L. P. & Goodwin, A. L. Structural characterisation of amorphous solid dispersions: Via metropolis matrix factorisation of pair distribution function data. Chem. Commun. 55, 13346–13349 (2019). 55. Sinka, I. C., Burch, S. F., Tweed, J. H. & Cunningham, J. C. Measurement of density variations in tablets using X-ray computed tomography. Int. J. Pharm. 271, 215–224 (2004). 56. Turner, T. D. et al. Measuring the Particle Packing of l-Glutamic Acid Crystals through X-ray Computed Tomography for Understanding Powder Flow and Consolidation Behavior. Cryst. Growth Des. 20, 4252–4263 (2020). 57. Tolba, E. et al. High biocompatibility and improved osteogenic potential of amorphous calcium carbonate/vaterite. J. Mater. Chem. B 4, 376–386 (2016). 58. Lunt, A. J. G. et al. Residual strain mapping through pair distribution function analysis of the porcelain veneer within a yttria partially stabilised zirconia dental prosthesis. Dent. Mater. 35, 257–269 (2019). 59. Lunt, A. J. G., Chater, P. & Korsunsky, A. M. On the origins of strain inhomogeneity in amorphous materials. Sci. Rep. 8, 1574 (2018). 60. Was, G. S. et al. Emulation of reactor irradiation damage using ion beams. Scr. Mater. 88, 33–36 (2014). 61. Pellin, M. J. et al. MeV per nucleon ion irradiation of nuclear materials with high energy synchrotron X-ray characterization. J. Nucl. Mater. 471, 266–271 (2016). 62. Sun, P. et al. Characterization of defect clusters in ion-irradiated tungsten by X-Ray diffuse scattering. J. Nucl. Mater. 510, 322–330 (2018). 63. Shahbudin, S. N. A., Othman, M. H., Amin, S. Y. M. & Ibrahim, M. H. I. A Review of Metal Injection Molding- Process, Optimization, Defects and Microwave Sintering on WC-Co Cemented Carbide. in IOP Conference Series: Materials Science and Engineering 226, 012162 (Institute of Physics Publishing, 2017). 64. DebRoy, T. et al. Scientific, technological and economic issues in metal printing and their solutions. Nat. Mater. 18, 1026–1032 (2019). 65. Eckel, Z. C. et al. Additive manufacturing of polymer-derived ceramics. Science (80-. ). 351, 58–62 (2016). 66. Sun, J., Yu, T., Xu, C., Ludwig, W. & Zhang, Y. 3D characterization of partially recrystallized Al using high resolution diffraction contrast tomography. Scr. Mater. 157, 72–75 (2018).

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7. Expressions of interest and support from the community Here we will briefly summarise a few of the 121 strong statements of support μ15 received from notable academics and industrialists from within the UK and internationally, covering science areas identified in §0. 7.1 Academic support Chemistry and catalysis: Sir Richard Catlow FRS states μ15 “is a very important development for materials chemistry generally and catalytic science in particular”. Russell Morris FRS affirms it “will be a step change in our ability to probe the structure of both the framework materials and the guest molecules inside”. Iain McCulloch FRS states it “will be an invaluable tool for characterising amorphous/poorly ordered thin films”. Energy materials: Clare Grey FRS stated μ15 “will enable my group to perform a range of electrochemical operando experiments with spatial resolution, a vital capability that is presently missing in the UK […]”. Peter Bruce FRS confirmed μ15 “will be of great benefit to battery research” as the techniques “[…] will reveal the complete structural picture and provide insight that will support the development of [new] technologies”. Advanced materials: Mark Senn recognises that “the ability to collect 3D-PDF on relatively small crystals will be transformative in understanding the nature of the correlated Jahn-Teller distortions, that are notoriously difficult to probe via […] other local probe[s]”. Silvia Ramos adds “[t]he ability to measure charge density and 3D pair correlation functions […] will be valuable for my research on charge ordered materials”. Earth and environment: Neil Hyatt says μ15 “will enable us to make new advances in the field of radioactive waste management” by studying “[…] crystalline and amorphous phases with the required spatial resolution to understand their mechanism and potentially kinetics of formation”. Jennifer Readman adds μ15 “will help enormously in understanding the structure-property relationships in [waste ion exchange materials]”. Pharmaceuticals: Gareth Williams says “XRD and PDF-CT mapping and 3D-dPDF could permit us to learn much more […] about the molecular rearrangements [in pharmaceuticals]”. Sven Schroeder would use μ15 to “study of the formation of organic solid solutions […to] help optimise their properties in pharmaceutical and agrochemical formulations” and emphasised complementary to soft X-ray imaging and spectroscopy. Materials engineering: Howard Stone said μ15 will “enable new insights […] into the crystallographic variations that exist across interfaces within engineering alloys[,…] the mechanistic origins of alloy performance and, importantly, how it changes under conditions of applied stress and temperature”. Kun Yan is keen to use μ15 “to investigate engineering materials with heterogeneous structures”. In summary, Matthew Rosseinsky FRS says “The transformative impact on our understanding of temporal and spatial correlations in the complex solid state that [μ15] will offer is sure to generate impact[…]” and J Paul Attfield FRS concludes “This would be my highest priority upgrade of the list”. 7.2 Industry support Chemistry and catalysis: Robert Dorner of BASF has used XRD-CT “to better understand ageing mechanisms in automotive catalysts” and recognises that “[a]ccess to such a resource within the UK should furthermore strengthen the UK as a center of internal excellence in scientific research”. James Patterson of BP states that “[i]t is only with capability like [μ15] that the next generation of catalyst processes will be developed”. Energy materials: Christina Jordy of SAFT recognises that μ15 would “allow us to better understand amorphous phases formed at the points of interfacial contact[s…] in all solid state Li-ion batteries”. Tim Hyde of Johnson Matthey concluded μ15 would “be a transformative instrument for JM in from diverse fields of in situ batteries […], electrocatalysis, catalysts, pharmaceuticals, materials chemistry, and fuel cells”. Pharmaceuticals: Fabia Gozzo of Excelsus Structural Solutions said PDF-CT “would allow us to analyze formulated [nanocrystalline and amorphous] drugs [within] capsules or tablets”, for which they “foresee important applications in the field of Intellectual Property […]”. Cheryl Doherty of GSK confirms “exploration of amorphous phases […] offers a useful route to explain, describe and control such systems”. 22

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7.3 Statements of support summary

Total number of submissions: 121

Key for Respondent's primary field of statements in Percentage of respondents research Appendix A Chemistry 50.0%

Materials Sciences 30.3% Energy 9.0% Engineering & Technology 4.1%

Physics 4.1% Earth Sciences & Environment 2.5%

Respondent location Percentage of respondents UK 79.5% International 20.5%

Type of organisation supporting Percentage of respondents Academic 82.0% Industry 9.8% Government 7.4% Research Institute 0.8%

Diamond user status Percentage of respondents Currently a user at Diamond 86.1% Not currently a user at Diamond 13.9%

7.4 Engagement webinar summary

Date of webinar: Monday 2nd November 2020 Number of attendees: 99

Attendee location Percentage of attendees UK 63.5% International 36.5%

8. Appendix A

The following pages are all 121 of the Statements of Support submitted for the I15 upgrade to μ15.

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