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Dept. of Modern Physics, University of Science and Technology of China, Hefei 230027, Anhui, China
Abstract. The neoclassical and double tearing modes have been analyzed with
related new phenomena in the reversed magnetic shear tokamak plasmas. The
instability threshold, and the linear and nonlinear evolution are derived
for the neoclassical tearing modes. It is found that the perturbed bootstrap
current in the resistive layer has a stabilizing effect while the
equilibrium bootstrap current in the outer region can destabilize the modes.
The dispersion relation is derived for the double tearing mode. It is found
that the onset of ``annular crash'' is due to the fast reconnection of
the hot and cold islands, triggered by the interaction of both branches. The
onset of ``core crash'' is mainly due to the coalescence between the hot
islands, triggered by the explosive growth of the inner branch.
IAEA 2001
