Very Long Pulse Testing of the TH 1506B 118 GHz Gyrotron for the ECRH Experiment on Tore Supra
C. Darbos, F. Bouquey, M. Lennholm, R. Magne, Ch. Portafaix
E. Giguet, Y. Legoff, Ch. Lievin
Thales Electron Devices
S. Alberti, J.P. Hogge
Association Euratom-Confédération Suisse
Forschungszentrum Karlsruhe, Institut für Hochleistungsimpuls- und Mikrowellentechnik, P.O. Box 3640, D-76021 Karlsruhe, Germany
An ECRH (Electron Cyclotron Resonance Heating) system capable of delivering 2.4 MW in pulses of 210 s is presently under construction at CEA Cadarache, for the Tore Supra experiment, to provide plasma heating and current drive by Electron Cyclotron Resonance interaction. The system will be made of six gyrotrons connected to the tokamak through six sets of corrugated waveguides and an antenna consisting of several mirrors, independently steerable, both in the toroidal and the poloidal direction.
The gyrotron TH 1506B has been developed thanks to a collaboration between TED (Thales Electron Devices formerly Thomson Tubes Electroniques), the Association Euratom-CEA and the Association Euratom-Confédération Suisse for use on both Tokamaks Tore Supra and TCV. The main features of this tube are: frequency 118 GHz, output power 400 kW for pulse length 210 s (500 kW for 5 s). The first series tube is presently under test for very long pulses within the facilities of CEA Cadarache; it is connected to a CW dummy load through a 15 meter-long transmission line and six miter-bends. A pulse duration of 110 s with an output power in the load not exceeding 300 kW has already been obtained. This pulse length has been observed to be limited by a strong degassing within the tube, presumably due to the overheating of the mirror box on which dissipated power of about 10 kW has been measured. Then this tube has been tested in the premises of the EPFL, with a quite simplified set-up (5 meter-long waveguide, one miter-bend and the dummy load already used for the factory acceptance test where 500 kW were obtained for 5 s) which pointed out that the limitation of power is neither due to the CEA particular set-up nor to a possible reflection of the load (which could be at the origin of the high losses in themirror box), but to the tube itself. More investigations at the CEA Cadarache with long pulses are now in progress, as well as calculations on the thermal behaviour of the mirror box and studies on possible improvement of its cooling.
Als Vortrag: 26th Int. Conf. on Infrared and Millimeter Waves, Toulouse, Sept. 10-14, 2001