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Abstract

The far-infrared interferometer system of Tokamak à Configuration Variable (TCV) has recently been extended. 14 vertical chords are now available and the measurement of the Faraday rotation induced by the poloidal magnetic field has been implemented. The method first developed and applied uses a rotating elliptical polarization of the probing beam but incurs the loss of the time resolution on the simultaneous interferometric measurements. The rotation of the polarization causes a perturbation of the line integrated density signal, disturbing the real-time density feedback of TCV. To avoid this inconvenience involves composing the probing beam of a beam with a rotating linear polarization and another beam with constant linear polarization. This leaves the simultaneous interferometric measurements undisturbed. The method was tested successfully in a tabletop experiment achieving a resolution of about 0.3 degrees Faraday rotation. The optical setup on TCV is designed such that it can easily be switched between the original and the improved method. First measurements of the Faraday rotation on elongated TCV plasmas are reported. The experimental sensitivity of the instrument is discussed in order to estimate the capabilities of the polarimeter on electron cyclotron resonance (ECR) heated TCV plasmas.

Additional information

Authors: BARRY S, Centre de Recherches en Physique des Plasmas, Association EURATOM � Confédération Suisse, Ecole Polytechnique Fédérale de Lausanne (CH);NIESWAND C, Centre de Recherches en Physique des Plasmas, Association EURATOM � Confédération Suisse, Ecole Polytechnique Fédérale de Lausanne (CH);HOFMANN F, Centre de Recherches en Physique des Plasmas, Association EURATOM � Confédération Suisse, Ecole Polytechnique Fédérale de Lausanne (CH)
Bibliographic Reference: Article: 1998 International Congress on Plasma Physics, 25th EPS Conference on Controlled Fusion and Plasma Physics, Prague (CZ), June 29 � July 3, 1998
Record Number: 199811277 / Last updated on: 1998-10-27
Category: PUBLICATION
Original language: en
Available languages: en
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