Simulation of edge-localized modes in a spherical tokamak: effects of ion diamagnetic drift

摘要

This paper presents the numerical modeling of nonlinear magnetohydrodynamic (MHD) instabilities containing the effects of finite Larmor radius (FLR) in spherical tokamak geometry. Our results contain the comparison of small, intermediate, and large effects of the FLR. For small values, the linear and nonlinear behavior is not greatly modified, but with intermediate and large FLR, stabilizing effects on the higher wave number components are observed in the linear phase but in the nonlinear phase the overall properties are dominated by MHD effects. Similar filamentary structures are reproduced as found in some of the experimental observations as a result of the development of ballooning modes. The formation and the properties of filamentary type structures during edge-localized modes are also discussed.