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2001
It is shown that plasma waves need not have an asymmetric spectrum in order to produce an electric current in a plasma embedded in a curved magnetic field. For instance, in a toroidal plasma, up–down asymmetric electron–cyclotron heating drives a toroidal current even if there is no net wave–particle momentum transfer and the wave field does …
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2001
Alfvén spectra in a reversed-shear tokamak plasma with a population of energetic ions exhibit a quasiperiodic pattern of primarily upward frequency sweeping (Alfvén cascade). Presented here is an explanation for such asymmetric sweeping behavior which involves finding a new energetic particle mode localized around the point of zero magnetic shear…
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2001
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2001
Detailed measurements of the rotation profile in L-mode plasmas heated by ICRF only (H minority in D), show a distinct off-axis maximum in the co-current direction. There is a slight dependence on the position of the resonance layer: the off-axis maximum in the rotation profile is modestly higher for a high field side position of the resonance laye…
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2001
First physics results are presented from MAST (Mega-Amp Spherical Tokamak), one of the new generation of purpose built spherical tokamaks (STs) now commencing operation. Some of these results demonstrate, for the first time, the novel effects of low aspect ratio, for example, the enhancement of resistivity due to neo-classical effects. H-mode is ac…
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2001
Gyrokinetic theory is used to investigate the effect of the polarization drift on magnetic island evolution. Three regimes are found. For island phase velocities between the ion- and electric-drift velocities, the polarization current is shown to be stabilizing. For phase velocities between the electric- and electron- drift velocities, the island e…
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2001
The VULCAN [C. N. Danson et al. , Opt. Commun. 103 , 392 (1993)] laser at the UK Central Laser Facility is being used for laboratory-based simulations of collisionless shocks. By ensuring that key dimensionless parameters in the experiments have values similar to those of supernova remnants (SNRs), the hydrodynamics and magnetic field of the experi…
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2001
A region of zero current density in the plasma center has been observed in the advanced tokamak scenarios with off-axis lower-hybrid current drive in the JET and JT-60U tokamak experiments. Significantly, the central current density does not become negative, although this is expected based on conventional current diffusion. In this paper, it is sho…
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2001
The polarization current plays an important role in the evolution of magnetic islands with a width comparable to the characteristic ion orbit width. Understanding the evolution of such small magnetic islands is important for two reasons: (1) to investigate the threshold mechanisms for growth of large-scale islands (e.g., neoclassical tearing modes)…
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2001
The surfatron offers the possibility of particle acceleration to arbitrarily high energies, given a sufficiently large system. Surfatron acceleration of electrons by waves excited by ions reflected from supernova remnant (SNR) shocks is investigated using particle simulations. It is shown that surfatron and stochastic acceleration could provide a s…
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