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UKAEA-CCFE-PR(19)372019
The diffusion of defects in crystalline materials governs macroscopic behaviour in a wide range of processes, including alloying, precipitation, phase transformation, and creep. In real materials, intrinsic defects are unavoidably bound to static trapping centres such as impurity atoms, meaning that their diffusion is controlled by the de-trapping …
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UKAEA-RACE-PR(19)012019
Systems Engineering (SE) allows addressing the design of complex systems from a holistic standpoint, starting from the early stage of development until the end of its lifetime. Using a SE approach, all the stakeholders’ needs can be considered, and different design alternatives can be proposed, taking into account requirements coming from all the…
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UKAEA-CCFE-PR(19)362019
Ti-containing micro-alloyed steels are often alloyed with molybdenum (Mo) to gain superior ageing-resistance through reduced nano-precipitate coarsening, although the exact mechanism is still disputed. Using small angle neutron scattering (SANS), we characterize precipitate composition and coarsening in Ti micro-alloyed steels with and without M…
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UKAEA-CCFE-PR(19)352019
We analyse spherical nanoindentation of single crystal copper using two different indenter tips of radii 7.4 and 27 um. The surface deformation surrounding the indents was measured using atomic force microscopy and the elastic rotation fields under the indents were measured using electron diffraction and transmission techniques. Using the measured …
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UKAEA-CCFE-PR(19)342019
Reduced models coupled to time-dependent axisymmetric vacuum field calculations are used to develop the prefill and feed-forward coil current targets required for reliable direct induction (DI) startup on the new MA-class spherical tokamaks, MAST-U and NSTX-U. The calculations are constrained by operational limits unique to each device, such as the…
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UKAEA-CCFE-PR(19)322019
The novel technique of dynamical mode decomposition (DMD) is applied to the outputs of a numerical simulation of Kelvin-Helmholtz turbulence in a cylindical plasma, so as to capture and quantify the time evolution of the dominant nonlinear structures. These structures comprise rotationally symmetric deformations together with spiral patterns, which…
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UKAEA-CCFE-PR(19)312019
Tungsten, a plasma-facing material for future fusion reactors, may be exposed to air during abnormal operation or accidents. Only limited information is available on the evolution of related oxide phases. This work addresses the effect of substrate orientation on structural variations of tungsten oxides. Annealing experiments in an argon-oxygen atm…
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UKAEA-CCFE-PR(19)302019
Alfven eigenmodes driven by energetic particles are routinely observed in tokamak plasmas. These modes consist of poloidal harmonics of shear Alfven waves coupled by inhomogeneity in the magnetic field. Further coupling is introduced by 3D inhomogeneities in the ion density during the assimilation of injected pellets. This additional coupling modi…
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UKAEA-CCFE-PR(19)292019
Two high purity tungsten powders, produced via different manufacturing techniques, were characterized to determine size distribution, morphology, thermal properties and flow characteristics and thus, the likely suitability for Laser Powder Bed Fusion (LPBF) production. Specimens from duplicate builds were produced with the two powders and character…
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UKAEA-CCFE-PR(19)282019
We study the amplitude modulation of the radial electric field constructed from the Langmuir probe plasma potential measurements at the edge of MAST. The Empirical Mode Decomposition technique is applied, which allows us to construct fluctuations on temporal scales of plasma turbulence, the Geodesic Acoustic Mode and these associated with the res…
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