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(CD2/EX9/5) Current Profile Modification with Electron Cyclotron Current Drive in the DIII-D Tokamak

   
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
 
M. E. Austin 
University of Texas at Austin, Austin, Texas
 
F. W. Baity Jr. , M. Murakami 
Oak Ridge National Laboratory, Oak Ridge, Tennessee
 
S. Bernabei , K.-L. Wong 
Princeton Plasma Physics Laboratory, Princeton, New Jersey
 
G. Giruzzi 
Association EURATOM-CEA, Centre d'Etudes Nucleaires de Cadarache, Cadarache, France
 
R. W. Harvey 
CompX, Del Mar, California
 
B. W. Rice 
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.

 

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