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The density profile of fusion plasmas can be investigated by the reflectometry diagnostic. The measurement principle is based on radar techniques which calculate the phase shift of a millimetre wave propagating into the plasma and reflected at a cut-off layer. However, this propagation is perturbed by the plasma turbulence. This study attempts to describe the density fluctuation effects upon the detected signal in order to understand the mechanisms which sometimes prevent the measurement of phase. The first part of the work is a study of the mechanisms and the origin of the turbulence which is responsible for phase disturbance. The second part of this work is the development and the use of a new heterodyne reflectometer. This new diagnostic uses O-mode beam polarization and works in the 26 GHz to 36 GHz frequency range. The heterodyne reflectometer developed offers several advantages of different distinct reflectometry techniques (ie fast sweep, absolute and differential phase measurement, heterodyne detection).

Additional information

Authors: MOREAU P, Université Aix-Marseille I (FR)
Bibliographic Reference: Report: EUR-CEA-FC-1618 FR (1997) 209pp.
Availability: Available from Association Euratom-CEA, CEN Cadarache, 13108 Saint-Paul-lez-Durance (FR)
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