Modification of the Current Profile in DIII-D by Off-Axis Electron Cyclotron Current Drive Page: 4 of 13
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MODIFICATION OF THE CURRENT PROFILE IN DIII-D
T.C Luce et al. BY OFF-AXIS ELECTRON CYCLOTRON CURRENT DRIVE
Modification of the Current Profile in DIII-D
by Off-Axis Electron Cyclotron Current Drive
T.C. Luce, Y.R. Lin-Liu, R.W. Harvey,' G. Giruzzi,2 J.M. Lohr,
C.C. Petty, P.A. Politzer, R. Prater, and B.W. Rice3
General Atomics, P.O. Box 85608, San Diego, California 92186-5698
1CompX, 12839 Via Grimaldi, Del Mar, California 92014
2CEA, Centre d'Etudes de Cadarache, F-13108 Saint Paul lez Durance, France
3Lawrence Livermore National Laboratory, Livermore, California 94551-9900
Localized non-inductive currents due to electron cyclotron wave absorption have been
measured on the DIII-D tokamak. Clear evidence of the non-inductive currents is seen on
the internal magnetic field measurements by motional Stark effect spectroscopy. The
magnitude and location of the non-inductive current is evaluated by comparing the total and
Ohmic current profiles of discharges with and without electron cyclotron wave power. The
measured current agrees with Fokker-Planck calculations near the magnetic axis, but exceeds
the predicted value as the location of the current drive is moved to the half radius.
Control and sustainment of the current profile by non-inductive means is key element
of the DIII-D tokamak research program. To realize a practical advanced tokamak scenario,
it appears necessary to maintain the current profiles which are created by transient means in
order to sustain the high levels of fusion performance. In the absence of any demonstrated
pressure profile control to manipulate the bootstrap current, direct current drive is required.
Non-inductive current drive by electron cyclotron waves (ECCD) is the technique planned
for advanced tokamak demonstration on DIII-D. ECCD has several advantages for DIII-D
which carry forward to a future fusion power plant. The location and localization of the
current drive is determined by the illumination of the cyclotron resonance by the launched
waves. The location can be controlled almost independently of the plasma parameters by
GENERAL ATOMICS REPORT GA-A23167
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Luce, T.C.; Lin-Liu, Y.R.; Harvey, R.W.; Giruzzi, G.; Lohr, J.M.; Petty, C.C. et al. Modification of the Current Profile in DIII-D by Off-Axis Electron Cyclotron Current Drive, article, July 1, 1999; San Diego, California. (digital.library.unt.edu/ark:/67531/metadc722747/m1/4/: accessed December 11, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.