STATUS OF THE 1MW, 140GHZ, CW GYROTRON FOR W7-X
C. Liévin1, S. Alberti2, A. Arnold3,4, E. Borie3, G. Dammertz3, V. Erckmann5, E. Giguet1,
R. Heidinger3, J.P. Hogge2, S. Illy3, W. Kasparek6, K. Koppenburg3,4, M. Kuntze3,
H. Laqua5, G. Le Cloarec1, F. Legrand1, W. Leonhardt3, R. Magne7, G. Michel5,
G. Müller6, G. Neffe3, B. Piosczyk3, M. Schmid3, M. Thumm3,4, M.Q. Tran2
1
Thales Electron Devices, 2 rue Latécoère, F-78141 Vélizy-Villacoublay, France2
Centre de Recherche en Physique des Plasmas, Association Euratom-Confédération Suisse,EPFL Ecublens, CH-1015 Lausanne, Suisse
3
Forschungszentrum Karlsruhe, Association Euratom-FZK, IHM,Postfach 3640, D-76021 Karlsruhe, Germany
4
Universität Karlsruhe, Institut für Höchstfrequenztechnik und Elektronik,Kaiserstrasse 12, D-76128 Karlsruhe, Germany
5
Max-Planck-Institut für Plasmaphysik (IPP), Walter-Rathenaustrasse 49a,D-17489 Greifswald, Germany
6
Institut für Plasmaforschung, Universität Stuttgart, Pfaffenwaldring 31,D-70569 Stuttgart, Germany
7
Association Euratom-CEA, Département de Recherche sur la Fusion Contrôlée,13108 Saint Paul-lez-Durance Cédex, France
In the framework of a collaboration between FZK-Karlsruhe, CRPP-Lausanne and TED-Vélizy, with contributions from IPF-Stuttgart, CEA-Cadarache and IPP Garching/Greifswald, a 1 MW, 140 GHz, CW gyrotron for the 10 MW ECRH system of the new stellarator experiment Wendelstein 7-X at IPP Greifswald (Germany) is under development.
The tube operates in the TE28,8 cavity mode and provides a linearly polarised, fundamental Gaussian output beam. It is composed of a diode-type electron gun, an improved beam tunnel, a high-mode-purity low-ohmic-loss cavity with rounded transitions, an optimised non-linear uptaper, a highly efficient internal quasi-optical mode converter employing an improved launcher together with one quasi-elliptical and two beam shaping reflectors, a large single-stage depressed collector with beam shaping and sweeping magnets, and a horizontal RF output through a large-aperture, water edge-cooled, single-disk CVD-diamond window.
A first tube has been tested at FZK. In short pulse operation and at a beam current of 40 A, an output power of 1.15 MW was achieved with an accelerating voltage of 84 kV and a depression voltage of 25 kV (49% efficiency). RF mode purity measurements performed using an IR camera and a thin dielectric target located at different positions across the RF beam showed a very good agreement with the theoretical predictions. After long pulse conditioning of the gyrotron and auxiliaries, the following record performances were finally achieved: 1 MW – 10s (efficiency of 50 %), 0.9 MW – 45 s (efficiency of 39 %), 0.74 MW – 100 s (efficiency of 32 %), 0.64 MW – 140 s and 0.47 MW – 180 s. Power modulation experiments performed on a few seconds pulses with modulation frequencies up to 50 kHz showed the gyrotron capability to operate from 0.1 to 1 MW.
The tube has then been sent back to TED for completion of an detailed expertise prior to the fabrication of an improved prototype which will have been tested by end of August 2002.
als Vortrag:
22 nd SOFT, Helsinki, Finnland, 9-13 Sept. 2002