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T. C. Luce, Y. R. Lin-Liu, J. Lohr,
C. C. Petty, R. Prater, R. W. Callis, J. S. deGrassie,
R. I. Pinsker, D. Ponce
DIII-D National Fusion Facility, General Atomics, San Diego,
California 92186-5608
University of Texas at Austin, Austin, Texas
Oak Ridge National Laboratory, Oak Ridge, Tennessee
Princeton Plasma Physics Laboratory, Princeton, New Jersey
Association EURATOM-CEA, Centre d'Etudes Nucleaires de Cadarache,
Cadarache, France
CompX, Del Mar, California
Lawrence Livermore National Laboratory, Livermore, California
M. Zerbini
ENEA, Magnetic Confinement Fusion Physics, Rome, Italy
Abstract. Proof-of-principle
experiments on the suitability of electron cyclotron current drive (ECCD) for
active current profile control are reported. Experiments with second harmonic
extraordinary mode absorption at power levels near 1 MW have demonstrated
ability to modify the current profile. This modification is manifested in
changes in the internal inductance and the time at which sawteeth
appear. Measurements of the local current density and internal loop voltage
using high resolution motional Stark effect spectroscopy to half of the minor
radius in discharges with localized deposition clearly demonstrate localized
off-axis ECCD at the predicted location. Comparison with theory indicates the
detrimental effect of trapped electrons on the current drive efficiency is
less than predicted. Modification of the theory for finite collisionality is
the leading candidate to explain the observations.
IAEA 2001
