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UKAEA-CCFE-PR(23)1692023
The Grad–Shafranov equation for axisymmetric MHD equilibria is a nonlinear, scalar PDE which in principle can have zero, one or more non-trivial solutions. The conditions for the existence of multiple solutions has been little explored in the literature so far. We develop a simple analytic model to calculate multiple solutions in the large asp…
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UKAEA-CCFE-PR(23)1672023
A nonlinear 4-dimensional drift island theory derived in (Imada et al 2019 Nucl. Fusion 59 046016 and references therein) provides qualitative predictions of the plasma response to a stationary neoclassical tearing mode (NTM) magnetic island in a low beta, large aspect ratio tokamak plasma. (Dudkovskaia et al 2021 Plasma Phys. Control. Fusion 63 05…
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UKAEA-CCFE-PR(23)1632023
High resolution D2 Fulcher band spectroscopy was used in the MAST-U divertors during Super-X and elongated conventional divertor density ramps with D2 fuelling from the mid-plane high-field side. In the Super-X case (density ramp from Greenwald fraction 0.12 to 0.24), the upper divertor showed ground state rotational tempe…
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UKAEA-CCFE-PR(23)1512023
Multiphase Fe-based hardfacing alloys, for example Tristelle 5183 Fe-21%Cr-10%Ni7.5%Nb-5%Si-2%C in wt.%, are extensively used for tribological applications, including valves, bearings and drive mechanisms, where two surfaces are unavoidably subjected to loaded sliding contact within engineering systems. In this study, transmission electron microsco…
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UKAEA-CCFE-CP(23)612021
The relative role of particle transport and edge fuelling in setting the H-mode density pedestal is still a key open question [1]. Although reduced pedestal models have proven successful in predicting the pedestal pressure for a wide range of plasma scenarios [2,3,4], they lack a first principle based, predictive model for the edge density. Pred…
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UKAEA-CCFE-PR(23)1602022
The reduced activation ferritic/martensitic steel Eurofer 97 is employed by many concept designs for the plasma-facing first wall of the EU DEMO fusion reactor. These designs feature precision joints between Eurofer 97 coolant piping for which novel laser-keyhole welding is one proposed technique. In this work, the microstructure of laser-keyhol…
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UKAEA-CCFE-PR(23)1562023
Heat sinks have manifold applications, from micro-electronics to nuclear fusion reactors. Their performance expectations will continue to increase in line with the power consumption and miniaturisation of technology. Additive manufacturing enables the creation of novel, compact heat sinks with greater surface-to-volume ratios and geometrical comple…
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UKAEA-CCFE-PR(23)1552023
Shear flows in turbulent fluids have been known to act as transport barriers for some time. An example of a shear flow generating mechanism is the E×B shear in plasma, which has a substantial impact on the dynamics of magnetic confinement fusion devices. The influence of this may be seen in the scrape-off layer (SOL) where blobs or filaments may b…
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UKAEA-CCFE-PR(23)1492022
Materials subjected to irradiation damage often undergo local changes in the microstructure that effect the expected performance. To investigate those changes, this work proposes a novel approach to detect strain localisation caused by irradiation-induced damage in nuclear materials on the microstructural level, conside…
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UKAEA-CCFE-PR(23)1422023
A Supervised Parallel Optimisation (SPO) is presented. The proposed framework couples different optimisation algorithms to solve single-objective optimisation problems. The supervision balances the exploration and exploitation capabilities of the distinct optimisers included, providing a general framework to solve problems with diverse character…
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