Neoclassical Theory of Pedestal Flows and Comparison with Alcator C-Mod Measurements

Neoclassical theory of pedestal flows and comparison with Alcator C-Mod measurements

Neoclassical implications of the strong radial electric field, inherently present in an H-mode tokamak pedestal, are considered. The main ion poloidal flow in the pedestal is predicted to be reduced in magnitude, or even reversed, compared with its core counterpart. The resulting change in the neoclassical formula for the impurity flow is shown to result in improved agreement with boron measure...

H-mode Pedestal Studies in Alcator C-mod

H-mode Pedestal Characteristics and Mhd Stability of the Edge Plasma in Alcator C-mod

Under most operational conditions of Alcator C-Mod the dominant type of H-mode is the steady state enhanced Dα mode (EDA), characterized by good energy confinement, continuously degraded impurity confinement and absence of regular ELMs. In this regime a quasicoherent (QC) electromagnetic mode (kθ~5 cm, f~100 kHz) is observed, localized in the region of the density pedestal. Experimental evidenc...

Modification of H-mode pedestal structure with lower hybrid waves on Alcator C Mod

The application of lower hybrid waves (LH) in H-mode plasmas on Alcator C-Mod can result in significant reduction of core particle inventory, with no significant degradation of energy confinement. This phenomenon has been observed in steady enhanced Dα (EDA) H-mode targets, which are sustained by ion cyclotron RF auxiliary heating, in which pedestal density nped is usually tied firmly to plasma...

Magnetic Topology Effects on Alcator C-Mod Flows

The effect of magnetic topology on ion and impurity flows in a tokamak is considered by investigating the consequences of (i) the reversal of toroidal and poloidal magnetic fields and currents, (ii) a switch from lower to upper X-point operation, (iii) poloidal magnetic field or plasma current reversal, and (iv) toroidal magnetic field reversal. The general symmetries associated with magnetic t...