UKAEA Papers

Showing 1741 - 1750 of 1892 UKAEA Paper Results
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…

Published
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…

Published
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…

Published
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…

Published
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…

Published
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)…

Published
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…

Published
2001

In conventional neoclassical theory, the density and temperature gradients are not allowed to be as steep as frequently observed in the tokamak edge. In this paper the theory of neoclassical transport in a collisional, impure plasma is extended to allow for steeper profiles than normally assumed. The dynamics of highly charged impurity ions then be…

Published
2001

High confinement [with H 1 , ITERH- 98 y, 2 ] at b N 2.3 has been found in ASDEX Upgrade discharges with existing m, n 3, 2 neoclassical tearing modes (NTMs). The reason for the high confinement at high b N values is a transition of the NTMs into the so-called frequently interrupted regime. In this regime, the NTM growth is frequently interrupted b…

Published