The selective laser melting process is a promising large-scale additive manufacturing (or 3D printing) technique that allows for rapid production of prototypes, and lately for weight-sensitive/multi-functional parts at small volumes, with almost arbitrary complexity. The process builds the final parts layer-upon-layer by going through three main stages during each cycle: (1) deposition of a layer of fine powder (with a typical grain size of approximately 0.03 mm) on a fabrication surface to form a thin bed of powder, which is only marginally thicker than the average grain size; (2) a laser beam then melts the powder bed at specific locations, based on a 3D computer model of the final product; (3) the powder grains then fuse at those locations after cooling and solidifying to produce a layer of the final product. In general, the selective laser melting process and additive manufacturing provide several advantages compared to conventional manufacturing techniques, such as greater design freedom, mass customisation and personalisation of products, production of complex geometries to improve performance and reduce labour costs, decreased wastage of precious materials, and new business models and supply chains. However, several challenges also exist. For example, a lack of understanding of the impact of powder grain shape on the underlying physical processes has forced the industry to require the majority of individual powder grains to be spherical. Such a stringent requirement increases the cost of powder (raw material), which consequently increases the production cost and hinders the development of new processes and the introduction of new materials. To address this issue, high-quality research software for process simulation is required to complement experiments and to enable new scientific discoveries and innovations. The present research programme addresses this technological need by providing a novel computational package capable of modelling various complex physical phenomena underlying the selective laser melting process. To achieve this, high-performance computing will be used to track the motion of individual grains in the system, their interaction with a laser beam, and their phase changes. This computational package will then be used to uncover the complex impact of powder grain shapes on the absorption and scattering of a laser beam within the bed and the following rapid melting process. Furthermore, it is hypothesised that elongated or satellite-spherical particles with small inclusions on their surfaces (grain shapes which are commonly present in powders and are generally considered undesirable) can, in fact, improve the process if their number densities are carefully selected. This hypothesis will be tested here for the first time, which can greatly reduce the cost of raw materials for selective laser melting, which results in wider adoption of this enabling technology.

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When a beam of fast, high energy electrons are injected into an undulating magnetic field (often called a 'wiggler'), they are forced to oscillate perpendicular to their direction of propagation and to emit light at the electron oscillation frequency. As this mixture of electrons and light propagates along the wiggler, the electrons begin to 'bunch' at the same wavelength as the light and act in unison to generate high brightness coherent light. When this happens it is called a Free Electron Laser (FEL). When the electrons are accelerated to speeds just below the speed of light, the electrons can emit X-ray light. This has a very short wavelength and can be used to make images of very small objects such as atoms. If the X-rays can be made into very short pulses, they can also take images of atoms without blurring - just like using the flash on a camera in a dark room. Most computer codes that simulate this FEL interaction make simplifications in the process which allows faster computation times. However, these simplifications mean that some information about the process is lost. This lost information is necessary if one wants to simulate e.g. very short light pulse generation. This proposal includes the lost information in a computer simulation code 'PUFFIN' which allows new methods to be investigated to improve the quality of the light emitted by the FEL. In addition, we will connect up PUFFIN with other simulation codes that allow the full FEL to be modelled from the start of the electron acceleration through to their exit at the end of the FEL. These 'start-to-end' simulations are important as they can allow different electron accelerators to be tested as drivers of the FEL, and can model their different characteristics. One such accelerator of current interest is the plasma accelerator which can be much smaller than current Radio-Frequency accelerators used to drive FELs. Use of plasma accelerators would significantly reduce the cost of FELs and make then more accessible to a wider group of scientists. PUFFIN is useful as it can model electron beams from plasma accelerators much better than other simulation codes. Keeping the extra information contained in the PUFFIN simulations, and linking it up with other simulation codes, results in a powerful FEL simulator that can model effects such as very short pulse generation and plasma accelerator drivers of FELs. This ability opens up many new areas for research to improve the light output from FELs. With these improvements would come the ability to investigate new areas of science that have until now been closed to us. These areas differ hugely, from observing how viruses and potential new drugs penetrate the membranes of living cells to creating conditions in the laboratory similar to those at the centre of Jupiter and Saturn. The improvements to simulating the FEL process using PUFFIN have the potential to have a real and large impact on such fundamental scientific knowledge. Furthermore, this fundamental knowledge can play a crucial role in developing new products and processes that will help economies, society and the environment.

The selective laser melting process is a promising large-scale additive manufacturing (or 3D printing) technique that allows for rapid production of prototypes, and lately for weight-sensitive/multi-functional parts at small volumes, with almost arbitrary complexity. The process builds the final parts layer-upon-layer by going through three main stages during each cycle: (1) deposition of a layer of fine powder (with a typical grain size of approximately 0.03 mm) on a fabrication surface to form a thin bed of powder, which is only marginally thicker than the average grain size; (2) a laser beam then melts the powder bed at specific locations, based on a 3D computer model of the final product; (3) the powder grains then fuse at those locations after cooling and solidifying to produce a layer of the final product. In general, the selective laser melting process and additive manufacturing provide several advantages compared to conventional manufacturing techniques, such as greater design freedom, mass customisation and personalisation of products, production of complex geometries to improve performance and reduce labour costs, decreased wastage of precious materials, and new business models and supply chains. However, several challenges also exist. For example, a lack of understanding of the impact of powder grain shape on the underlying physical processes has forced the industry to require the majority of individual powder grains to be spherical. Such a stringent requirement increases the cost of powder (raw material), which consequently increases the production cost and hinders the development of new processes and the introduction of new materials. To address this issue, high-quality research software for process simulation is required to complement experiments and to enable new scientific discoveries and innovations. The present research programme addresses this technological need by providing a novel computational package capable of modelling various complex physical phenomena underlying the selective laser melting process. To achieve this, high-performance computing will be used to track the motion of individual grains in the system, their interaction with a laser beam, and their phase changes. This computational package will then be used to uncover the complex impact of powder grain shapes on the absorption and scattering of a laser beam within the bed and the following rapid melting process. Furthermore, it is hypothesised that elongated or satellite-spherical particles with small inclusions on their surfaces (grain shapes which are commonly present in powders and are generally considered undesirable) can, in fact, improve the process if their number densities are carefully selected. This hypothesis will be tested here for the first time, which can greatly reduce the cost of raw materials for selective laser melting, which results in wider adoption of this enabling technology.

The process of crystal nucleation from solution requires, as its initial stage, separation of solute and solvent molecules and simultaneous formation of molecular clusters in order to create a new, nano scale, phase which can subsequently grow to become a crystal. Elucidating the fundamental physics and chemistry that govern the structure of this nucleation transition state remains one of the truly unresolved 'grand challenges' of the physical sciences. Individual nucleation events are localised in space but rather infrequent on the time-scale of a molecular vibration making both experimental detection and molecular modelling of the process difficult. In addition to this, available experimental techniques provide data averaged over both time and space so that extracting insights into the nucleation process may only be achieved through a combination of experiment and modelling. We propose a novel approach to this problem in which we scrutinise the crystallisation of two related molecular systems in hitherto unprecedented depth, building on established state-of-the-art experimental and computational techniques, but combining these, for the first time, with in situ synchrotron radiation (SR) X-ray scattering and spectroscopy methodologies capable of probing long range and local electronic and geometric structure at molecular resolution. Our hypothesis is that, by utilising appropriate experimental conditions, applying these state of the art time resolved scattering and spectroscopic techniques and building cluster models that are consistent with macroscopic features of the systems studied (crystal morphology, polymorphic form, solution chemistry, crystal growth rates), we can deduce a structural model of a nucleation event from the change in averaged solution structure as a function of increasing solution supersaturation and time. We thus expect incisive structural information for every step of the nucleation process: measured molecular scale properties can be used to confront computational predictions at molecular, supra-molecular and solid-state levels, so that the structural and size parameters for the nucleation pathway are revealed. A step change in our understanding of this area of science is thus expected.