Mechanisms of the Plasma Rotation Effect on the Type-I ELM in Tokamaks

Full text: Mechanisms of the plasma rotation effect on the type-I ELM related MHD modes are investigated numerically. To clarify them, a new energy is defined, which relates to the potential energy without the contribution of the Doppler shift. By resolving this energy into each component that includes the rotation effect on the equilibrium and that on the displacement of the MHD mode, it is found that the MHD mode is destabilized by the difference between the eigenmode frequency and the equilibrium toroidal rotation frequency. This destabilizing mechanism is essentially induced by the rotation with steep shear, and becomes effective as the wavelength of the MHD mode becomes shorter. Based on these results, a toroidal rotation effect on the type-I ELM is investigated numerically in JT-60U H-mode plasmas. This analysis shows that the sheared toroidal rotation can have impact on the achievable pressure gradient and type-I ELM behavior in JT-60U by changing the MHD stability. (author)