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FIR polarimetry is a well-tried technique for time-resolved measurements of magnetic fields in tokamak plasmas. On the basis of well-developed and routinely employed FIR interferometers, appropriate instruments have been constructed for various machines. However, the data analysis aiming at detailed poloidal magnetic field distribution is rather involved and the results are sensitive to ad hoc assumptions about the shape and shift of the magnetic flux surfaces. On the other hand, qualitative information on the related current density profile and especially on its response to operational measures during a discharge is readily available by real-time conversion of polarimetric data into suitable shape parameters. Furthermore the signals provide fairly accurate information on the location of the magnetic axis and lend themselves to controlling the plasma position in the vacuum vessel. Thus, besides its somewhat limited potential for high-precision measurements of local magnetic fields, FIR polarimetry can be a valuable supplement to the commonly applied set of monitor and control diagnostics.

Additional information

Authors: SOLTWISCH H, Institut für Plasmaphysik, Kernforschungsanlage Jülich GmbH, Jülich (DE)
Bibliographic Reference: Article: Proceedings of the 4th International Symposium on Laser-Aided Plasma Diagnostics (1989) pp. 278-283
Record Number: 199010794 / Last updated on: 1994-12-01
Original language: en
Available languages: en