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IAEA-CN77
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(EX5/1) Physics of Confinement Improvement of Plasmas with Impurity Injection in DIII-D

M. Murakami1), G. R. McKee2), G. L. Jackson3), G. M. Staebler3), D. A. Alexander4), D. R. Baker3), G. Bateman5), L. R. Baylor1), J. A. Boedo6), N. H. Brooks3), K. H. Burrell3), J. R. Cary4)7), R. H. Cohen8), R. J. Colchin1), J. C. DeBoo3), E. J. Doyle9), D. R. Ernst10), T. E. Evans3), C. Fenzi2), C. M. Greenfield3), D. E. Greenwood1), R. J. Groebner3), J. Hogan1), W. A. Houlberg1), A. W. Hyatt3), R. J. La Haye3), R. Jayakumar8), T. C. Jergigan1), R. A. Jong8), J. E. Kinsey5), A. H. Kritz5), L. L. Lao3), C. J. Lasnier8), M. A. Makowski8), A. Messiaen11), J. Mandrekas12), R. A. Moyer6), J. Ongena11), A. Pankin5), T. W. Petrie3), C. C. Petty3), C. L. Rettig9), T. L. Rhodes9), B. W. Rice8), D. W. Ross13), J. C. Rost14), S. Shasharina4), W. M. Stacey12), H. E. St John3), P. Strand1), R. D. Sydora15), T. S. Taylor3), D. M. Thomas3), M. R. Wade1), R. E. Waltz3), W. P. West3), K. L. Wong10), L. Zeng9), and the DIII-D Team
 
1) Oak Ridge National Laboratory, Oak Ridge, Tennessee USA
2) University of Wisconsin, Madison, Wisconsin USA
3) General Atomics, P.O. Box 85608, San Diego, California USA
4) Tech-X Corporation, Boulder, Colorado USA
5) Lehigh University, Bethlehem, Pennsylvania USA
6) University of California, San Diego, California USA
7) University of Colorado, Boulder, Colorado USA
8) Lawrence Livermore National Laboratory, Livermore, California USA
9) University of California, Los Angeles, California USA
10) Princeton Plasma Physics Laboratory, Princeton, New Jersey USA
11) KMS/ERM, Brussels, Belgium
12) Georgia Institute of Technology, Atlanta, Georgia USA
13) University of Texas, Austin, Texas USA
14) Massachussetts Institute of Technology, Cambridge, Massachusetts USA
15) University of Alberta, Edmonton, Canada

Abstract.  External impurity injection into L-mode edge discharges in DIII-D has produced clear increases in confinement (factor of 2 in energy confinement and neutron emission), reduction in all transport channels (particularly ion thermal diffusivity to the neoclassical level), and simultaneous reduction of long-wavelength turbulence. Suppression of the flux wavelength turbulence and transport reduction are attributed to synergistic effects of impurity-induced enhancement of ExB shearing rate and reduction of toroidal drift wave turbulence. A prompt reduction of density fluctuations and local transport at the beginning of impurity injection appears to result from an increased gradient of toroidal rotation enhancing the ExB shearing. Transport simulations carried out using the National Transport Code Collaboration Demonstration Code with a GyroLandau fluid model, GLF23, indicate ExB shearing suppression is the dominant transport suppression mechanism.

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IAEA 2001