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UKAEA-CCFE-PR(18)102018
In Ion-Temperature-Gradient (ITG) driven turbulence, the resonance condition leads to ion particle turbulent transport coefficients significantly larger than electron particle turbulent transport coefficients. This is shown in non-linear gyrokinetic simulations and explained by an analytical quasilinear model. It is then illustrated by JETTO-QuaLi…
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UKAEA-CCFE-PR(18)32018
Recent studies have shown that on JET with the Be/W ITER-like wall (JET-ILW) in high beta discharges with high D2 gas rates the inter-ELM temperature pedestal growth is saturated half way through the ELM cycle, leading to plasmas with reduced confinement, and that the linear MHD stability of these pedestals is inconsistent with the Peeling-Ballooni…
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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)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(16)542016
The recently proposed set of zeroth-order moment equations to model poloidal density asymmetries induced by temperature anisotropies in rotating tokamak plasmas (R. Bilato et al., Nuclear Fusion 54 (2014) 072003) is here extended to account for the effects of the localization of the ion cyclotron (IC) resonance on the poloidal inhomogeneity of the …
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CCFE-PR(16)452016
It is shown that ITG turbulence close to the threshold exhibits a long time behaviour, with smaller heat fluxes at later times. This reduction is connected with the slow growth of long wave length zonal flows and, consequently, the numerical dissipation on these flows must be sufficient small. Close to the nonlinear threshold for turbulence generat…
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CCFE-PR(15)892015
The interplay between toroidal rotation u, parallel flow shear u? and perpendicular flow shear ?E in the stabilisation of tokamak turbulence is investigated in non-linear flux-tube gyrokinetic simulations with the GKW code. The non-linear simulations are performed for a reference L-mode DIII-D plasma (the so-called shortfall case) at r/a = 0.8, var…
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CCFE-PR(15)882015
Verification is the fundamental step that any turbulence simulation code has to be submitted in order to assess the proper implementation of the underlying equations. We have carried out a cross comparison of three flux tube gyrokinetic codes, GENE [F. Jenko et al., Phys. Plasmas 7, 1904 (2000)], GKW [A. G. Peeters et al., Comput. Phys. Commun. 180…
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CCFE-PR(15)782015
The non-linear evolution of a magnetic island is studied using the Vlasov gyro-kinetic code GKW. The interaction of electromagnetic turbulence with a self-consistently growing magnetic island, generated by a tearing unstable >0 current profile, is considered. The turbulence is able to seed the magnetic island and bypass the linear growth phase b…
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CCFE-PR(15)442015
The effects of poloidal asymmetries and heated minority species are shown to be necessary to accurately describe heavy impurity transport in present experiments in JET and ASDEX Upgrade. Plasma rotation, or any small background electrostatic field in the plasma, such as that generated by anisotropic external heating can generate strong poloidal den…
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