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2014
Merging-compression start-up in the Mega Ampere Spherical Tokamak provides an opportunity to investigate the merging of flux ropes through magnetic reconnection, and the self-organization into a single flux rope, in a low-plasma-ß, high-Lundquist-number plasma. We present an overview of simulations of this process using the compressible Hall-MHD e…
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2014
ELM mitigation has been demonstrated in MAST using resonant magnetic perturbations (RMPs) with toroidal mode number, n RM P = 2, 3, 4, 6. It has been observed that the mitigated ELM frequency increases with the amplitude of the applied field provided it is above a critical threshold. This threshold value depends on the mode number of the RMP, with …
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2014
Using the recently-installed Fast-Ion Deuterium Alpha (FIDA) spectrometer, the effects of low-frequency (20 - 50 kHz) chirping energetic particle modes with toroidal mode number n = 1 on the NBI-driven fast-ion population in MAST plasmas are considered. Results from the FIDA diagnostic are presented and discussed in the light of the present theoret…
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2014
Variational principles are powerful tools in many branches of theoretical physics. Certain conservative systems which do not admit of a traditional Euler-Lagrange variational formulation are given a novel generalization. Illustrative examples, including the recently discovered scale-invariant analogue of the Korteweg-de Vries equation are presented…
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2013
In the merging-compression method of plasma start-up, two flux-ropes with parallel toroidal current are formed around in-vessel poloidal field coils, before merging to form a spherical tokamak plasma. This start-up method, used in the Mega-Ampere Spherical Tokamak (MAST), is studied as a high Lundquist number and low plasma-beta magnetic reconnecti…
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2013
New diagnostic, modelling and plant capability on the Mega Ampere Spherical Tokamak (MAST) have delivered important results in key areas for ITER/DEMO and the upcoming MAST Upgrade, a step towards future ST devices on the path to fusion currently under procurement. Micro-stability analysis of the pedestal highlights the potential roles of micro-tea…
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2013
Following recent observations suggesting the presence of the geodesic acoustic mode (GAM) in ohmically heated discharges in the Mega Amp Spherical Tokamak (MAST) [J. R. Robinson et al., Plasma Phys. Controlled Fusion 54, 105007 (2012)], the behaviour of the GAM is studied numerically using the two fluid, global code CENTORI [P. J. Knight et al. Com…
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2012
In this paper, current profiles for plasma discharges on the mega-ampere spherical tokamak are directly calculated from pickup coil, flux loop, and motional-Stark effect observations via methods based in the statistical theory of Bayesian analysis. By representing toroidal plasma current as a series of axisymmetric current beams with rectangular cr…
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2012
The transport of injected beam ions due to toroidal magnetic field ripple in the mega-ampere spherical tokamak (MAST) is quantified using a full orbit particle tracking code, with collisional slowing-down and pitch-angle scattering by electrons and bulk ions taken into account. It is shown that the level of ripple losses is generally rather low, al…
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2011
Showing 71 - 80 of 143 UKAEA Paper Results