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research article

Shear modulation experiments with ECCD on TCV

Cirant, S.
•
Alberti, S.  
•
Gandini, F.
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2006
Nuclear Fusion

Anomalous electron transport is determined by turbulence, which in turn is affected by magnetic shear. A novel application of electron cyclotron current drive (ECCD), aiming at localized shear modulation, has been applied on the TCV tokamak for experiments on shear-dependent electron transport. Pairs of EC beams, absorbed at the same radius, with one oriented for co- and the other for counter-injection, are modulated out of phase in order to force a local modulation of current-density at constant input power. Off-axis deposition (rho(dep) = 0.24) is performed to avoid the central region, where the low heat flux would make transport analysis difficult. In addition some sawteeth control is achieved in this way. A significant impact on local shear is achieved with I-ECCD approximate to 0. 1 I-OH, even when the modulation period is much shorter than the current diffusion time across the whole plasma radius. The main result is that although source (heat and particle) terms are constant, both electron density and temperature are modulated during alternated ECCD. Once equilibrium effects are taken into account for appropriate mapping of Thomson scattering measurements onto flux coordinates, modulation of T-e and electron pressure, peaked on-axis, is confirmed at all radii internal to EC deposition. The best confinement occurs for co-injection, in which case a local decrease (approximate to 55%) in the magnetic shear causes a decrease in the electron thermal diffusivity of a similar amount (approximate to 65%).

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Type
research article
DOI
10.1088/0029-5515/46/5/002
Web of Science ID

WOS:000238158400002

Author(s)
Cirant, S.
Alberti, S.  
Gandini, F.
Behn, R.  
Goodman, T.  
Nikkola, P.  
Date Issued

2006

Publisher

IOP Publishing Ltd

Published in
Nuclear Fusion
Volume

46

Issue

5

Start page

500

End page

511

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
CRPP  
SPC  
Available on Infoscience
April 16, 2008
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/22336
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