[Table of Contents]

Plasma and Fusion Research

Volume 3, S1057 (2008)

Regular Articles

Parametric Dependence of the Perpendicular Velocity Shear Layer Formation in TJ-II Plasmas
Luis GUIMARAIS, Teresa ESTRADA1), Enrique ASCASIBAR1), María E. MANSO, Luis CUPIDO, Tim HAPPEL1), Emilio BLANCO1), Francisco CASTEJON, Rubén Jimenez-GOMEZ1), María A. PEDROSA1), Carlos HIDALGO1), Ignacio PASTOR1) and Antonio Lopez-FRAGUAS1)
As. Euratom-IST, CFN, Instituto Superior Técnico, Lisbon, Portugal
1)
Laboratorio Nacional de Fusión. As. Euratom-CIEMAT, Madrid, Spain
(Received 16 November 2007 / Accepted 29 February 2008 / Published 4 August 2008)

Abstract

In TJ-II plasmas, the perpendicular rotation velocity of the turbulence changes from positive to negative (from ion to electron diamagnetic direction) inside the Last Closed Magnetic Surface (LCMS) when the line-averaged plasma density exceeds some critical value, this change being dominated by the inversion in the radial electric field. In this work we study the parameters that control the inversion in the perpendicular rotation. A parametric dependence of the critical density has been obtained studying plasmas confined in different magnetic configurations (different rotational transform and/or plasma volume) and heated with different ECH power levels. The studied data set shows a positive exponential dependence on heating power and a negative one on plasma radius, while the dependence on rotational transform has low statistical meaning. Besides, analysis of local plasma parameters points to plasma collisionality as the parameter that controls the inversion of the perpendicular rotation velocity of the turbulence.

Keywords

radial electric field, perpendicular rotation, turbulence, reflectometry, stellarator

DOI: 10.1585/pfr.3.S1057

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This paper may be cited as follows:

Luis GUIMARAIS, Teresa ESTRADA, Enrique ASCASIBAR, María E. MANSO, Luis CUPIDO, Tim HAPPEL, Emilio BLANCO, Francisco CASTEJON, Rubén Jimenez-GOMEZ, María A. PEDROSA, Carlos HIDALGO, Ignacio PASTOR and Antonio Lopez-FRAGUAS, Plasma Fusion Res. 3, S1057 (2008).