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Remote generation of magnetic islands in magnetised plasmas by turbulence

Author: Olivier Agullo
Requested Type: Poster Only
Submitted: 2015-01-19 13:11:02

Co-authors: O. Agullo, A. Poyé, M. Muraglia, S. Benkadda, N. Dubuit, X. Garbet, A. Sen

Contact Info:
Aix-Marseille Université
Av. E. N. Niemen
Marseille, Marseille   13397
France

Abstract Text:
Understanding reconnection phenomena in fusion devices such as ITER is an important issue for future fusion reactors. Indeed, magnetic reconnection can be problematic for burning and non-burning tokamak plasmas: tearing modes (neoclassical or otherwise) grow slowly expelling energetic particles from the plasma core and possibly lead to disruption phenomena that can terminate the discharge and cause damage to the plasma facing components. However, neoclassical tearing modes (NTM) require pre-existing seed islands to grow. While both (3,2) and (2/1) NTM magnetic islands are often triggered by sawtooth, ELM and 1/1 MHD precursors, magnetic islands can also appear without any noticeable MHD event. Thus, the origin of seed islands needed for the NTM growth, and, more specifacally, the impact of the turbulence on seed islands are still open questions for fusion reactors. Micro-scale turbulent fluctuations, zonal flows and MHD activity coexist in a plasma. The study of the interaction between turbulence and magnetic island is becoming an active field of investigation in the plasma community. However, there is still no clear experimental proof that both interact significantly together and, specifically, that turbulence can be at the origin of a strong MHD activity. Recently [1], by means of numerical nvestigations, it has been proposed a specific signature of turbulence driven magnetic islands which could be possibly used to demonstrate experimentally that island can be trigger by turbulence. We show by means of 3D fluid simualtions that edge/interchange turbulence could also trigger, remotely, (2/1) magnetic islands located in an inner region. It is found that island size could be larger than the NTM onset threshold in ITER context. We show also the existence of a predator-prey regime between ZF and Island in a turbuent medium.

[1] O. Agullo \textit{et al}, Phys. of Plasmas 21, 092303 (2014) DOI: 10.1063/1.4894699

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