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 components lifetime. Magnetic perturbation fields have shown their potential for control and mitigation these ELMs and are therefore an important topic of present research.

  The recently obtained preliminary results from the JET tokamak, the largest fusion experiment in the world, have shown that the size of ELMs can be significantly reduced without much degradation of plasma confinement by the application of a magnetic perturbation field generated by an external coil system. The heat loading has been reduced to an acceptable size for e.g. ITER. Our group belongs to the leading groups in this field based on our previous fundamental studies on TEXTOR and the promising results recently obtained at JET. Based on the first experimental results of ELM control on JET, important remaining open questions need to be addressed in order to gain confidence in this method, qualify the applicability and allow an up-scaling to the next generation of tokamaks.