VERY LONG PULSE OPERATION OF THE TORE SUPRA ECRH SYSTEM
C. Darbos(a), S. Alberti(b), F. Bouquey(a), J. Clary(a), E. Giguet(c), G. Giruzzi(a), M. Jung(a), M. Lennholm(a), C. Liévin(c), R. Magne(a), T. Petit(a), D. Roux(a), JL Segui(a), M. Thumm(d), M.Q. Tran(b), X. Zou(a)
(a) Association Euratom-CEA, CEA/DSM/DRFC, CEA-Cadarache,
13108 Saint Paul Lez Durance, France
(b)
Association Euratom-Confédération Suisse, Centre de Recherches en Physiques des Plasmas, EPFL-Ecublens, 1015 Lausanne, Switzerland(c)
Thales Electron Devices, 2 rue Latécoère, 78414 Vélizy-Villacoublay, France(d)
Association Euratom-FZK, IHM, Postfach 3640, 76021 Karlsruhe, GermanyAn ECRH (Electron Cyclotron Resonance Heating) system presently capable of coupling 800 kW for 5 s to the plasma of the Tore Supra Tokamak is under development at CEA (Commissariat à l'Energie Atomique) Cadarache. The aim is to increase the system performance to 3 MW for 5 s and to 2.4 MW for up to 600 s.
The main components of the generator (see [1] for the description of the whole system) are six gyrotrons TH 1506B developed in collaboration between European research laboratories and Thales Electron Devices (TED). The main features of this gyrotron are : frequency 118 GHz, output power 400 kW for pulse length up to 600 s and 500 kW for 5 s. The short pulse specification forms part of the factory acceptance test, while the long pulse capability is only tested at CEA Cadarache after delivery. Two gyrotrons have already been manufactured and tested on dummy loads and on plasma, individually and together. The first series tube has achieved a 110 s pulse on a water load, but with a limited output power of 300 kW. This limitation has been observed through a strong degassing within the tube due to the overheating of the internal mirror box. This overheating is presumably due to spurious oscillations within the injector of the gyrotron. New studies to prevent these oscillations and to improve the performance of the tube are ongoing. This work should lead to the manufacture of a new gyrotron by spring 2003. The two existing gyrotrons were connected to Tore Supra for a short experimental campaign at the end of 2001 and further plasma experiments are planned for 2002. The two gyrotrons were used independently and together for pulse lengths up to 2 s, injecting power under various toroidal and poloidal angles, various polarizations of the wave and for the first time, with a modulation frequency of the RF signal up to 25 Hz.
The different results both on dummy loads and on plasma are described in the paper, as well as some problems encountered mainly during the tests on plasma. Depending on the progress, studies on the modifications for the next gyrotron will also be presented.
[1] "The 118 GHz ECRH experiment on Tore Supra", C. Darbos et al. Fusion Engineering and Design 56-57 (2001) pp 605-609.