| Popis: |
The kinetic effects on the ideal ballooning and interchange/Mercier modes are studied in model equilibria for an L=2 heliotron, large helical device (LHD) [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)]. It is shown that the ion finite Larmor radius (FLR) effect stabilizes the modes with high toroidal mode number, n. On the other hand, the finite electron compressibility plays a double role, and stabilizes the low-n modes as the ideal magnetohydrodynamic (MHD) modes, while it destabilizes the high-n modes. It is discussed that the inclusion of the compressibility impacts the stability, and this effect is stronger in LHD than in a comparable tokamak, which is due to the larger magnitude of the local curvature. As a result of the competition between the FLR and the compressibility, it is shown in LHD that the low-n instabilities can become much weaker than that expected by the ideal MHD, while the high-n instabilities are prone to remain unstable near the plasma core region. |
