IDEAL MAGNETOHYDRODYNAMIC INSTABILITIES WITH LOW TOROIDAL MODE NUMBERS LOCALIZED NEAR AN INTERNAL TRANSPORT BARRIER IN HIGH-BETA(P), MODE PLASMAS IN THE JAPAN ATOMIC-ENERGY RESEARCH-INSTITUTE TOKAMAK-60 UPGRADE

Local steep pressure gradient generated near an internal transport bar rier drives a radially localized magnetohydrodynamic (MHD) instability with low toroidal mode number (n) in the high-Pp mode plasma in the J apan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) [Y. Koide et al., Phys. Plasmas 4, 1623 (1997)]. The instability occurs in the beta(p) regime lower than that for the beta(p)-collapse and its g rowth rate is of the order of the ideal MHD instability. By a linear a nalysis of ideal MHD stability, low n modes localized near the interna l transport barrier are found to be destabilized in the situation that the bootstrap current driven by the steep pressure gradient reduces t he local magnetic shear (s less than or equal to 0) where the safety f actor is right close to an integer value. (C) 1997 American Institute of Physics.