Enhancement of the Stabilization Efficiency of a Neoclassical Magnetic Island by Modulated Electron Cyclotron Current Drive in the ASDEX Upgrade Tokamak
- Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstrasse 2, D-85748 Garching (Germany)
- Forschungszentrum Karlsruhe, Association EURATOM-FZK, IHM, D-76021 Karlsruhe (Germany)
The efficiency of generating a helical current in magnetic islands for the purpose of suppression of neoclassical tearing modes (NTMs) by electron cyclotron current drive (ECCD) is studied experimentally in the ASDEX Upgrade tokamak. It is found that the efficiency of generating helical current by continuous current drive in a rotating island drops drastically as the width 2d of the co-ECCD driven current becomes larger than the island width W. However, by modulating the co-ECCD in phase with the rotating islands O point, the efficiency can be recovered. The results are in good agreement with theoretical calculations taking into account the equilibration of the externally driven current on the island flux surfaces. The result is especially important for large next-step fusion devices, such as ITER, where 2d>W is expected to be unavoidable during NTM suppression, suggesting that modulation capability should be foreseen.
- OSTI ID:
- 20861604
- Journal Information:
- Physical Review Letters, Vol. 98, Issue 2; Other Information: DOI: 10.1103/PhysRevLett.98.025005; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0031-9007
- Country of Publication:
- United States
- Language:
- English
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