State of the Art Neoclassical Tearing Mode Control in DIII-D Using Real-time Steerable Electron Cyclotron Current Drive Launchers
Authors: Egemen Kolemen, et. al.
Abstract:
Real time steerable electron cyclotron current drive (ECCD) has been
demonstrated to reduce the power requirements and time needed to remove 3/2 and 2/1
neoclassical tearing modes (NTM) in the DIII-D tokamak. In a world first demonstration of
the techniques required in ITER, the island formation onset is detected automatically,
gyrotrons are turned on and the real-time steerable ECCD launcher mirrors are moved
promptly to drive current at the location of the islands. This shrinks and suppresses the modes
well before saturation using real-time motional Stark effect (MSE) constrained equilibria
reconstruction with advanced feedback and search algorithms to target the deposition. In
ITER, this method will reduce the ECCD energy requirement and so raise Q by keeping the
EC system off when the NTM is not present. Further, in the experiments with accurate
tracking of pre-emptive ECCD to resonant surfaces, both 3/2 and 2/1 modes are prevented
from appearing with as little as one fourth the ECCD peak power required for removal of a
saturated mode.
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Submitted to: Nuclear Fusion (January 2014)
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Download PPPL-4978 (pdf 201 MB 22 pp)
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