Overview of Edge-Localized Mode Control in Tokamak Plasmas

The next generation of fusion machines like ITER and DEMO will need a reliable method for controlling the periodic transient expulsion of a considerable amount of energy onto the plasma-facing components caused by instabilities at the plasma edge. The good plasma confinement in these tokamak devices will result in a steepened pressure profile at the plasma edge. When the pressure gradient exceeds a critical value, so-called edge-localized modes (ELMs) are destabilized. These modes feature a periodic fast collapse of the edge pressure, a sudden loss of the confinement, and a subsequent release of heat and particles onto plasma-facing components. The associated transient heat loads might cause excess erosion and lead to a strong reduction of the plasma-facing component lifetime. In this lecture, an overview of recent development of several ELM control methods for next-generation tokamaks, e.g., ITER is given. Some key physics issues related to the mechanism of ELM control are discussed.