A. Thyagaraja
This paper and a forthcoming one develop the spectral theory of ballooning transformations relevant to tokamak physics from rst principles in a rigorous and yet intuitively clear manner. The power of the ballooning representation to throw light on the spectral characteristics of the plasma problems to which it is applicable is emphasized, and examp…
PublishedR. O. Dendy P. Helander
Self-organized criticality ~SOC! often features in sandpile-type modeling of complex systems such as magnetic fusion plasmas, but its observed role in real sandpiles is equivocal. Here, a probabilistic model displaying some of the observed phenomenology of real sandpiles is proposed. It generates avalanches involving particle loss that, like most e…
PublishedP. Helander
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…
PublishedD. A. Gates R. Akers L. Appel P. G. Carolan N. Conway et al.
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…
PublishedC. N. Lashmore-Davies V. Fuchs R. A. Cairns
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 (…
PublishedJ. W. Connor R. J. Hastie H. R. Wilson R. L. Miller
A new formalism for analyzing the magnetohydrodynamic stability of a limiter tokamak edge plasma is developed. Two radially localized, high toroidal mode number n instabilities are studied in detail: a peeling mode and an edge ballooning mode. The peeling mode, driven by edge current density and stabilized by edge pressure gradient, has features wh…
PublishedJ. B. Taylor J. W. Connor P. Helander
Transport barriers and transitions between modes of low and high confinement in tokamak plasmas are often attributed to suppression of turbulence by a shear flow related to a plasma gradient, e.g., of density. However, such shear flow is also affected by the second derivative of density. When this is introduced there is no unique relation between f…
PublishedR. D. Hazeltine P. Helander Peter J. Catto
The simplest nontrivial model of transport across a magnetic island chain in the presence of collisionless streaming along the magnetic field is solved by a Wiener–Hopf procedure. The solution found is valid provided the boundary layer about the island separatrix is narrow compared to the island width. The result demonstrates that when this assum…
PublishedP. Helander R. J. Hastie J. W. Connor
The bootstrap current in a non-Maxwellian tokamak plasma with electron cyclotron heating is calculated. The calculation is exact in the limit of highly charged ions, where pitch-angle scattering dominates over quasilinear diffusion, and shows that the current is entirely determined by the pressure of the trapped electrons. If the ion charge is fini…
Published