-
1999
-
1999
-
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 (…
-
1998
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…
-
1998
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…
-
1998
Bulk ion flow can be modified by ion–neutral interactions in the edge region of tokamaks where neutral atoms are abundant. In this region, the standard neoclassical expression for the ion flow is not consistent with the experimental observations. Previous work in the plateau regime [Valanju et al., Phys. Fluids B 4, 2675 (1992)] suggests that the…
-
1998
The edge plasma of a tokamak is affected by atomic physics processes and can have density and temperature variations along the magnetic field that strongly modify edge transport. A closed system of equations in the Pfirsch–Schluter regime is presented that can be solved for the radial and poloidal variation of the plasma density, electron and ion…
-
1998
Ion plasma flow and flow shear just inside the last closed flux surface of a tokamak can be strongly altered by neutral atoms and anomalous effects. For a collisional edge, neutrals modify the standard Pfirsch–Schluter expression for the parallel ion flow through the strong coupling provided by ion–neutral collisions. Even for rather small neut…
Showing 2431 - 2440 of 2537 UKAEA Paper Results