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Comparison of Impurity Poloidal Rotation in ECRH and NBI Discharges of the TJ-II HELIAC

B. Zurro, A. Baciero, D. Rapisarda, V. Tribaldos, TJ-II Team

Fusion Science and Technology / Volume 50 / Number 3 / October 2006 / Pages 419-427

Technical Paper / Stellarators /

The poloidal rotation of C V ions has been deduced, in the TJ-II stellarator, from spectral line shifts measured using a high-spectral-resolution spectrometer and a nine-fiber-channel system. Analysis of the data obtained has shown that a change of sign of the poloidal rotation direction occurs that depends abruptly on plasma density but is independent of the heating method. Whereas in low-density plasmas the poloidal direction corresponds to a positive radial electric field, at higher densities negative radial electric fields are deduced from the measured poloidal rotation. These measurements are in qualitative agreement with neoclassical theory calculations that predict a change in the sign of the radial electric field mainly because of a change in the ratio of the electron-to-ion temperature.

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