IT Chapman M-D Hua SD Pinches RJ Akers AR Field JP Graves RJ Hastie CA Michael The Mast Team
MAST plasmas with a safety factor above unity and a profile with either weakly reversed shear, or broad low shear regions, regularly exhibit long-lived saturated ideal magnetohydrodynamic (MHD) instabilities. The toroidal rotation is flattened in the presence of such perturbations and the fast ion losses are enhanced. These ideal modes, distinguish…
PublishedIT Chapman JP Graves C Wahlberg The Mast Team
The sensitivity of the stability of the ideal n = 1 internal kink mode to variations in the plasma profiles is analysed both analytically and numerically in rotating tokamak plasmas. These stability analyses have been carried out including the centrifugal effects of toroidal plasma rotation upon the equilibrium, and also inconsistently when the equ…
PublishedJ. P. Graves I. Chapman S. Coda L.-G. Eriksson T. Johnson
The sawtooth control mechanism in plasmas employing off-axis toroidally propagating ion cyclotron resonance waves in tokamaks is reinvestigated. The radial drift excursion of energetic passing ions distributed asymmetrically in the velocity parallel to the magnetic field determines stability when the rational q 1/4 1 surface resides within a narrow…
PublishedC. Wahlberg I. T. Chapman J. P. Graves
Analytical theory and two different magnetohydrodynamical stability codes are used in a study of the effects of toroidal plasma rotation on the stability of the ideal, internal kink mode in tokamaks. The focus of the paper is on the role that the centrifugal effects on the plasma equilibrium play for the stability of this mode, and results from one…
PublishedI. T. Chapman S. D. Pinches L. C. Appel R. J. Hastie T. C. Hender S. Saarelma S. E. Sharapov I. Voitsekhovitch J. P. Graves
Recent advances in modeling the effects of anisotropic energetic ion distributions have enabled the development of a complete coherent physics explanation of sawtooth stabilization in both conventional and spherical tokamaks. As an example, a complete model has been developed to explain the asymmetric stabilization of sawteeth with respect to neutr…
PublishedM. F. F. Nave H. R. Koslowski S. Coda J. Graves M. Brix R. Buttery C. Challis C. Giroud M. Stamp P. De Vries Jet-Feda Contributors
During a recent reversed toroidal field (B T) campaign at the Joint European Torus (JET), experiments were performed to investigate the effect on sawteeth of neutral beam injection (NBI)-driven toroidal plasma rotation counter to the direction of the toroidal plasma current and B T . A power scan at constant density has permitted analytical continu…
PublishedJ. P. Graves R. O. Dendy K. I. Hopcraft E. Jakeman
Recent measurements in tokamak plasmas provide clear evidence for rapid nondiffusive transport and non-Gaussian fluctuations, and have been widely interpreted in terms of the sandpile and self-organized criticality (SOC) paradigms. Many of the statistical physics inferences that can be drawn from observations of, for example, avalanching transport …
PublishedJ. P. Graves K. I. Hopcraft
The recent Joint European Torus deuterium-tritium campaign has yielded ion-cyclotron-resonanceheated (ICRH) pulses during which both the sawtooth characteristics and the ICRH minority ion population both evolve substantially. At multiple times during each pulse, the evolution of the kinetic-fluid MHD energy is calculated from measurement of the ene…
Published