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The relationship between the current density distribution and the electron density profile during the flat-top phase of ohmic discharges in TEXTOR has been investigated by means of far infrared interferometry and polarimetry. It is found that neither gradual nor rapid changes of the electron density distribution alter the current profile significantly. The conclusion is drawn from the temporal evolution of the measured Faraday rotation signals alpha(exp)(x,t). By taking into account the known variation of the density profile, but keeping the current distribution fixed, theoretical signals alpha(sim)(x,t) can be calculated which match the observed waveforms very well without any need to readjust the poloidal field. Under conditions of severe impurity contamination and additional ICR heating, alpha(exp)(x,t) and alpha(sim)(x,t) show systematic deviations indicative of flattened current density distributions.

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Authors: SOLTWISCH H, Forschungszentrum Jülich GmbH (KFA) (DE);KOSLOWSKI H R, Forschungszentrum Jülich GmbH (KFA) (DE)
Bibliographic Reference: Article: 21st EPS Conference on Controlled Fusion and Plasma Physics, Montpellier, 27 June - 1 July, 1994, Vol. 18B (1994) Part I, pp. 26-29
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