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UKAEA-CCFE-PR(19)092018
Kinetic treatments of drift tearing modes that match an inner, resonant layer solution to an external MHD solution, can fail to match the ideal MHD boundary condition on the parallel electric field. In this paper we demonstrate how consideration of ion sound and ion Landau damping effects achieves this, placing the theory on a firm footing. The …
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UKAEA-CCFE-PR(18)692018
The impact of the three-dimensional (3D) tokamak geometry from external magnetic perturbations (MPs) on the local edge stability has been examined in high confinement mode (H-mode) plasmas with edge localised modes (ELMs) in ASDEX Upgrade. The 3D geometry has been probed using rigidly rotating MP fields. The measured distortions of the plasma bound…
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UKAEA-CCFE-PR(18)612018
Effects of toroidal plasma flow, magnetic drift kinetic damping as well as feedback control, on the resistive wall mode instability in HL-2M tokamak are numerically investigated, using the linear stability codes MARS-F/K (Liu Y Q et al 2000 Phys. Plasmas 7 3681, Liu Y Q et al 2008 Phys. Plasmas 15…
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CCFE-PR(17)662017
The theory of stability and saturation of nonlinear ballooning modes in tokamaks is developed using a generalised Archimedes’ principle which is justified for thin elliptical flux tubes. The equation of motion in general geometry is derived and then applied to a simplified ‘s-a’ equilibrium and the nonlinear dynamics of this equilibr…
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CCFE-PR(16)472016
Resonant magnetic perturbations (RMP) have extensively been demonstrated as a plausible technique for mitigating or suppressing large edge localized modes (ELMs). Associated with this is a substantial amount of theory and modelling efforts during recent years. Various models describing the plasma response to the RMP fields have been proposed in the…
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CCFE-PR(16)192016
ELM control may be essential to develop ITER scenarios with a reasonable lifetime of divertor components, whilst ELM pacing may be essential to develop stationary ITER scenarios with a tungsten divertor. Resonant magnetic perturbations (RMPs) have mitigated ELMs in high collisionality plasmas in JET. The efficacy of RMPs in mitigating the ELMs is f…
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CCFE-PR(16)102016
The magnetic perturbations produced by the resonant magnetic perturbation (RMP) coils will be rotated in ITER so that the spiral patterns due to strike point splitting which are locked to the RMP also rotate. This is to ensure even power deposition on the divertor plates. VMEC equilibria are calculated for different phases of the RMP rotation. It i…
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CCFE-PR(17)192016
An explanation of the observed improvement in H-mode pedestal characteristics with increasing core plasma pressure or poloidal beta, pol b , as observed in MAST and JET, is sought in terms of the impact of the Shafranov shift, D¢ , on ideal ballooning MHD stability. To illustrate this succinctly, a self-consistent treatment of the low magnetic she…
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CCFE-PR(15)1012015
Tokamaks are traditionally viewed as axisymmetric devices. However this is not always true, for example in the presence of saturated instabilities, error fields, or resonant magnetic perturbations (RMPs) applied for edge localized mode (ELM) control. We use the VMEC code (Hirshman and Whitson 1983 Phys. Fluids 26 3553) to …
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CCFE-PR(15)452015
The role of anisotropic thermal diffusivity on tearing mode stability is analysed in general toroidal geometry following similar techniques to Glasser et al [A H Glasser, et al, Phys. Fluids 18 (1975) 875], although a stronger ordering of the plasma compressibility is required. Resistive layer equations are obtained for a resistive MHD model with a…
Showing 31 - 40 of 58 UKAEA Paper Results