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Local transport barrier formation and relaxation in reverse-shear plasmas on the Tokamak Fusion Test Reactor

Authors :
P. C. Efthimion
G. L. Schmidt
E. J. Synakowski
S. H. Batha
F. M. Levinton
A. T. Ramsey
Gregory W. Hammett
R. E. Bell
Robert Budny
E. Mazzucato
G. Taylor
G. Rewoldt
Michael A. Beer
T.S. Hahm
B.P. LeBlanc
C. E. Bush
Hyeon K. Park
M. C. Zarnstorff
M.G. Bell
S. D. Scott
Source :
Physics of Plasmas. 4:1736-1744
Publication Year :
1997
Publisher :
AIP Publishing, 1997.

Abstract

The roles of turbulence stabilization by sheared E×B flow and Shafranov shift gradients are examined for Tokamak Fusion Test Reactor [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)] enhanced reverse-shear (ERS) plasmas. Both effects in combination provide the basis of a positive-feedback model that predicts reinforced turbulence suppression with increasing pressure gradient. Local fluctuation behavior at the onset of ERS confinement is consistent with this framework. The power required for transitions into the ERS regime are lower when high power neutral beams are applied earlier in the current profile evolution, consistent with the suggestion that both effects play a role. Separation of the roles of E×B and Shafranov shift effects was performed by varying the E×B shear through changes in the toroidal velocity with nearly steady-state pressure profiles. Transport and fluctuation levels increase only when E×B shearing rates are driven below a critical value that is comparable to the fastest line...

Details

ISSN :
10897674 and 1070664X
Volume :
4
Database :
OpenAIRE
Journal :
Physics of Plasmas
Accession number :
edsair.doi...........2ad9f5ae97733783fe6beeab69c0ea7d