Effect of curvature in the magnetic shear profile on micro-tearing modes in the tokamak pedestal

摘要: The pedestal region of a tokamak plasma differs from the core in several respects. This work emphasizes magnetic shear profile which is distinctive for two reasons: close to magnetic-field separatrix so that q-profile intrinsically steep, and steep gradients cause peak bootstrap current with obvious effects on q(r). In fact, has complicated structure yielding curved profile. Global linear simulations suggest such could substantially affect nature micro-instabilities. paper analytically investigates this special feature pedestal, after appropriately modifying slab-model field equations allow more variation parallel wave vector. Surprisingly, departure locally q (flat shear), even when small, supports qualitatively novel mode whose width fixed by curvature unstable; its substantial growth rate robust sense persisting modification assumed be small. However, mode, originating details q-profile, will not found typical local ballooning gyrokinetic simulation.