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Abstract

Reflectometry is a powerful technique to measure density profile and density fluctuations in plasmas. It records the phase delay induced by the propagation of a probing wave reflecting at a cutoff layer into the plasma. For magnetic fusion application, probing frequencies varies between 10 GHz up to 200 GHz.
On Tore-Supra, a high field large size tokamak (B = 3.8 T, major radius: 2.4 m), four reflectometers are in operation. They are built on the same microwave scheme: a low frequency source (12-20 GHz), active frequency multipliers and heterodyne detection.
Three reflectometers covering the range 50 to 155 GHz in extraordinary polarization measure the density profile from the outer edge to the centre. At high magnetic field (B > 3.5 T), the whole profile, up to the inner edge, can be determined. In standard operation mode, measurements are recorded during the whole plasma discharge and the profiles are calculated automatically. A burst mode allows highly repetitive measurements to follow fast profile evolution like pellet or massive helium injection. Reflectometry is also sensitive technique for detecting Magneto Hydro Dynamic (MHD) modes. MHD tearing modes have been localized with the fast-swept reflectometers in agreement with magnetic surface reconstruction. Toroidal Alfven Eigenmodes have been observed in Ion Cyclotron resonance Heated (ICRH) plasmas.
The density fluctuations are investigated using different reflectometry techniques for complementary measurement. With fixed frequency measurements, fluctuations at low radial wave number are measured with high sensitivity, allowing the detection of Geoacoustic modes (GAM) in the plasma core. A new technique using repetitive fast frequency sweeps has been validate to measure the profile of density fluctuations with profile reflectometers. The fluctuation level is in agreement with fluctuation measurement using fixed frequencies.

Additional information

Authors: SABOT R, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);CLAIRET F, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);GIACALONE J C, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);MOLINA D, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);SIRINELLI A, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);VERMARE L, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);HENNEQUIN P, LPTP, Ecole Polytechnique, Palaiseau (FR);HONORÉ C, LPTP, Ecole Polytechnique, Palaiseau (FR);TRUC A, LPTP, Ecole Polytechnique, Palaiseau (FR);HEURAUX S, LPMIA, Université Henri Poincaré, Vandoeuvre (FR);LECLERT G, LPIIM, Université de Provence, Marseille (FR)
Bibliographic Reference: An oral paper given at: International Conférence PLASMA - 2005 on Research and Applications of Plasmas Organised by: Committee of Physics of the Polish Academy of Sciences (PL) Held at: University of Opole, Opole (PL)
Availability: Available from Association EURATOM-CEA, Département de Recherches sur la Fusion Contrôlée, CEA Cadarache, F-13108 St Paul-Lez-Durance, France Tel: (+33) 4 42 25 70 01; Fax: (+33) 4 42 25 64 21 E-mail: dirdrfc@drfc.cad.cea.fr
Record Number: 200518357 / Last updated on: 2005-10-04
Category: PUBLICATION
Original language: en
Available languages: en