Divertor effects on the stability of axisymmetric modes and kink modes in a tokamak
- 1 October 1988
- journal article
- Published by IOP Publishing in Nuclear Fusion
- Vol. 28 (10), 1859-1869
- https://doi.org/10.1088/0029-5515/28/10/013
Abstract
Stability against axisymmetric modes and free boundary n = 1 kink modes in a nearly circular tokamak with a poloidal divertor is investigated by using the linear ideal MHD code ERATO-J. Perturbations localized near the plasma surface (divertor) are shown to reduce the growth rate of MHD modes. Although the local variation of the n-index is large because of the presence of an X-point, a wide stability window for axisymmetric modes similar to limiter configurations is obtained. The detailed characteristics of the axisymmetric stability depend on the position of the X-point in the poloidal plane and on the structure of the divertor coil system. The large shear near the plasma surface is effective in stabilizing free boundary n = 1 kink modes. This shear stabilization is sensitive to the details of the divertor geometry, such as the location and number of X-points, and to the plasma pressure. The dependence of the critical beta on the current profile is also discussed.Keywords
This publication has 13 references indexed in Scilit:
- Effects of magnetic separatrix and pressure pedestal on finite beta external kink–tearing modesPhysics of Fluids, 1986
- Regime of Improved Confinement and High Beta in Neutral-Beam-Heated Divertor Discharges of the ASDEX TokamakPhysical Review Letters, 1982
- Ideal magnetohydrodynamic theory of magnetic fusion systemsReviews of Modern Physics, 1982
- Equilibrium and axisymmetric stability of dee-shaped plasmas in Doublet IIINuclear Fusion, 1982
- Axisymmetric MHD stability of elongated tokamaksNuclear Fusion, 1978
- Hydromagnetic stability of tokamaksNuclear Fusion, 1978
- Positional Instabilities of a Plasma in a Tokamak with a Magnetic LimiterJapanese Journal of Applied Physics, 1976
- Positional Instabilities in a Tokamak with a Resistive ShellJapanese Journal of Applied Physics, 1975
- Plasma equilibrium in a TokamakNuclear Fusion, 1971
- Application of the Virial Theorem to Equilibria of Toroidal PlasmasPhysics of Fluids, 1964