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2009
Sawtooth behavior has been investigated in plasmas heated with off-axis neutral beam injection in ASDEX Upgrade [A. Herrmann and O. Gruber, Fusion Sci. Technol. 44 , 569 (2003)] and the Mega-Ampere Spherical Tokamak MAST [A. Sykes and et al. , Nucl. Fusion 41 , 1423 (2001)]. Provided that the fast ions are well confined, the sawtooth period is foun…
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2009
The stability of ion temperature gradient ITG modes and the quasilinear fluxes driven by them are analyzed in weakly collisional tokamak plasmas using a semianalytical model based on an approximate solution of the gyrokinetic equation, where collisions are modeled by a Lorentz operator. Although the frequencies and growth rates of ITG modes far fro…
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2009
Experiments on the Alcator C-Mod and JET tokamaks with identical values of nondimensional variables at the pedestal top are expected to have the same local plasma transport for a ratio > 4 in absolute size and thus can help to clarify other effects in pedestal formation. At the high and low fields (7.9 T, 1.4 T respectively) involved, natural-densi…
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2009
Several improvements to the MAST plant and diagnostics have facilitated new studies advancing the physics basis for ITER and DEMO, as well as for future spherical tokamaks. Using the increased heating capabilities PNBI ≤ 3.8 MWH-mode at Ip = 1.2 MA was accessed showing that the energy confinement on MAST scales more weakly with Ip and more strong…
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2009
One of the main operational aims of the MAST experiment [1] and the proposed MAST upgrade is to investigate possible mechanisms to control the q-profile and drive off-axis current. Experiments were carried out to determine the extent to which the q-profile may be modified using two different approaches, transient and steady-state. Transient effects…
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2009
‘Advanced tokamak’ (AT) scenarios were developed with the aim of reaching tokamak steady-state operation. They are designed to optimise the self-generated current, whilst also reaching sufficiently high plasma pressure to achieve optimal fusion reaction rates. AT scenarios exhibit non-monotonic to flat safety factor profiles (q, a measure of th…
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2008
In this Letter, the linear stability of the resistive wall modes (RWMs) in toroidal geometry for a reversed field pinch (RFP) plasma is studied. Three computational models are used: the cylindrical code ETAW , the toroidal MHD code MARS-F , and the CARMA code, able to take fully into account the effects of a threedimensional conducting structure wh…
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2008
A simple formula for predicting the width of a saturated island, formed as a consequence of tearing perturbation of linear force-free fields in cylindrical geometry, is derived. The formula makes it possible to calculate the saturated island width in terms of the values of parameters characterizing the initial force-free equilibrium and can be appl…
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2008
Studies establishing key phenomena and developing diagnostics for energetic particle physics, which are essential for the next step burning plasma experiments such as the International Thermonuclear Experimental Reactor (ITER), have been performed at the Joint European Torus (JET). Experiments have demonstrated clear selfheating of deuterium-tritiu…
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2008
The Integrated tokamak modelling taskforce was set up to provide the European scientific community with simulation tools for preparing and analysing discharges of fusion experiments. We will report on recent progress made on the taskforce project on equilibrium and linear stability. A generic data structure has been devised to describe the geometry…
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