Effect of magnetic topology on MHD and transport in magnetic confinement fusion

Effect of magnetic topology on MHD and transport in magnetic confinement fusion Y. Liang *Forschungszentrum Jülich GmbH, IEK-4, 52425 Jülich, GermanyCurrently, the most advanced concepts for fusion confinement are the tokamak and the stellarator. The former is toroidally symmetric and 2D; the latter is a 3D device with a smaller degree of symmetry. The tokamak scheme is currently a leading variant for plasma confinement and is therefore being used for the ITER design and is planned for the DEMO reactor. It has recently been realized that 3D magnetic topology effects also play a significant role in this 2D concept. The results obtained from various tokamaks have shown that magnetic field perturbations can either completely suppress edge localized modes (ELMs), trigger small ELMs during ELM free periods, or affect the frequency and size of the type- ELMs in a controllable way, preserving good global energy confinement [1,2]. Although the physic s mechanism is still unclear, experimental results from those different devices demonstrate that the magnetic topology plays a key role in plasma confinement [3], edge MHD stability [4], and interactions between the plasma and the first wall, particularly with the divertor [5-7]. Recently, 3D magnetic topology effects form one of the hottest topics in fusion research today, and understanding them is essential for the success of future fusion devices. In this paper, an overview of physics understanding of various 3D effects on major MHD activities, i.e. tearing modes and edge - localized modes, [5-7], and plasma edge [8] and divertor transports [9-11] in magnetically confined plasmas will be presented . In addition, comparing the advantages and disadvantages of 2D and 3D magnetic topology effects in magnetic confinement fusion will be discussed