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G. M. Staebler, R. E. Waltz, and C. M. Greenfield
General Atomics, P.O. Box 85608, San Diego, California 92186-5608
B. W. Stallard
Lawrence Livermore National Laboratory, Livermore, California
Abstract. A comparison of two types of DIII-D plasmas with improved core ion
thermal transport is made. One is an H-mode edge weak magnetic shear discharge
and the other is an L-mode edge negative central shear plasma. It is found
that the region of reduced ion thermal transport is consistent with the region
where theory predicts stability of ion temperature gradient modes in both
cases. The electron thermal transport remains anomalously high throughout the
plasma. The electron transport may be caused by the presence of electron
temperature gradient modes in the outer part of the plasma. The modes are
found to be linearly unstable even into the region of high
E×B
shear. In the central core no drift-ballooning modes are found to be
unstable. The negative central shear case is predicted to be unstable to
resistive interchange modes in the reversed shear region.
IAEA 2001
