Effect of toroidal plasma flow and flow shear on global magnetohydrodynamic MHD modes

TLDR

The study investigates how a subsonic toroidal flow affects the linear MHD stability of a tokamak plasma with an external resistive wall. A non‑self‑adjoint eigenvalue problem for general kink and tearing modes is formulated and solved numerically for high‑β tokamaks. The results show that toroidal flow combined with plasma dissipation can open a stability window for the external wall, allowing stable beta values that exceed Troyon scaling predictions, and numerical computations using experimental data agree well with observations.

Abstract

The effect of a subsonic toroidal flow on the linear magnetohydrodynamic stability of a tokamak plasma surrounded by an external resistive wall is studied. A complex non-self-adjoint eigenvalue problem for the stability of general kink and tearing modes is formulated, solved numerically, and applied to high β tokamaks. Results indicate that toroidal plasma flow, in conjunction with dissipation in the plasma, can open a window of stability for the position of the external wall. In this window, stable plasma beta values can significantly exceed those predicted by the Troyon scaling law with no wall. Computations utilizing experimental data indicate good agreement with observations.