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CCFE-PR(17)552017
High Entropy Alloys (HEAs) is a fascinating field of research, with an increasing number of new alloys discovered. This would hardly be conceivable without the aid of materials modeling and the computational alloy design to investigate the immense compositional space. The simplicity of the microstructure achieved contrasts with the enormous complex…
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CCFE-PR(17)472017
Heavy impurities, such as tungsten (W), can exhibit strongly poloidally asymmetric density profiles in rotating or radio frequency heated plasmas. In the metallic environment of JET, the poloidal asymmetry of tungsten enhances its neoclassical transport up to an order of magnitude, so that neoclassical convection is expected to dominate over turbul…
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CCFE-PR(17)602017
Reciprocating Mach probe data is used to estimate the radial wave number of oscillatory zonal flows in Ohmic MAST plasma. An intermittent 10kHz mode is detected in the wavelet decomposition and windowed spectra of plasma potential fluctuations of the MAST tokamak edge plasma. Previously, this mode has been identified as a Geodesic Acoustic Mode (GA…
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CCFE-PR(17)422017
Quantitative comparisons are presented between gyrokinetic simulations and experimental values of the carbon impurity peaking factor in a database of JET H-modes during the carbon wall era. These plasmas feature strong NBI heating, hence high values of toroidal rotation and correponding gradient. Furthermore, the carbon profiles present particularl…
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CCFE-PR(17)542017
A nonlinear bump-on-tail model for the growth and saturation of energetic particle driven plasma waves has been extended to include two populations of fast particles - one dominated by dynamical friction at the resonance and the other by velocity space diffusion. The resulting temporal evolution of the wave amplitude and frequency depends on the re…
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CCFE-PR(17)432017
A potential threat to the performance of magnetically confined fusion plasmas is the problem of impurity accumulation, which causes the concentration of highly charged impurity ions to rise uncontrollably in the center of the plasma and spoil the energy confinement by excessive radiation. It has long been thought that the collisional transport of i…
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CCFE-PR(17)522017
The accumulation of impurities in the core of magnetically confined plasmas, resulting from standard collisional transport mechanisms, is a known threat to their performance as fusion energy sources. Whilst the axisymmetric tokamak systems have been shown to benefit from the effect of temperature screening, that is an outward flux of impurities dri…
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CCFE-PR(17)062017
Using an ab initio approach, we explore the stability of small vacancy and vacancychromium clusters in dilute body-centred cubic Fe-Cr alloys. To explain experimental observations described in C.D. Hardie et al., J. Nucl. Mater. 439, 33 (2013) and showing the occurrence of Cr segregation in low-Cr alloys, we investigate if chromium can form stable …
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CCFE-PR(17)112017
This work presents the first evidence of helical flow in RFX-mod q(a) < 2 tokamak plasmas. The flow pattern is characterized by the presence of convective cells with m = 1 and n = 1 periodicity in the poloidal and toroidal direction, respectively. A similar helical flow deformation has been observed in the same device when operatedfas a Reversed…
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CCFE-PR(17)122017
This paper presents for the first time a statistical validation of predictive TRANSP simulations of plasma temperature using two transport models, GLF23 and TGLF, over a database of 80 baseline H-mode discharges in JET-ILW. While the accuracy of the predicted Te with TRANSP-GLF23 is affected by plasma collisionality, the dependency of predictions o…
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