-
1999
A simple one-dimensional sandpile model is constructed which possesses exact analytical solvability while displaying both scale-free behavior and fractal properties. The sandpile grows by avalanching on all scales, yet its shape and energy content are described by a simple, continuous (but nowhere differentiable) analytical formula. The avalanche e…
-
1999
The ideal magnetohydrodynamic (MHD) stability of the tokamak edge is analyzed, with particular emphasis on radially localized instabilities; it is proposed that these are responsible for edge pressure gradient limits and edge localized modes (ELMS). Data and stability calculations from DIII-D [to appear in Proceedings of the 16th International Conf…
-
1999
Ion cyclotron emission (ICE) excited by collective instability of fusion a particles has been observed during deuterium-tritium experiments with radio-frequency heating and neutral beam injection (NBI) in the Joint European Torus. A model based on classical a-particle confinement is broadly consistent with this data. ICE spectra from discharges wit…
-
1999
-
1999
-
1999
Theoretical modeling of 1–2 MW positive hydrogen ion neutral injectors developed at Oak Ridge National Laboratory ~ORNL! has suggested that the plasma grid temperature could rise by up to 180 °C at pulse lengths above 0.5 s, leading to a grid deformation on the order of 5 mm, with a consequent change in focal length (from 4 to 2 m) and beamlet f…
-
1998
Theoretical and experimental work on the vertical position control system on the COMPASS-D tokamak is described. An analog proportional 1 derivative (P 1 D) system is currently used, and two important sources of disturbance are observed in the system. One source is 600-Hz noise from thyristor power supplies, and the other is impulselike disturbance…
-
1998
In a toroidally rotating tokamak plasma, heavy impurity ions accumulate on the outside of each flux surface under the action of the centrifugal force. The collision frequency therefore varies over the flux surface. This circumstance is shown to enhance the neoclassical transport processes, including the bootstrap current, by making collisions occur…
-
1998
The Small Tight Aspect Ratio Tokamak (START) [A. Sykes et al., Nucl. Fusion 32, 769 (1994)] spherical tokamak has recently achieved the record value of toroidal beta~30% in a tokamak-like configuration. The improvements that have made these results possible are presented along with a description of the global equilibrium parameters of the discharge…
-
1998
A theory of fast wave absorption in a high-beta plasma is given. A reduced, second-order, ordinary differential equation has been used which includes all collisionless electron dissipation mechanisms and ion cyclotron damping over many harmonics. This is relevant to the high-harmonic fast wave heating scheme proposed by Ono [Phys. Plasmas 2, 4075 (…
Showing 2471 - 2480 of 2581 UKAEA Paper Results