Prototype of a 1 MW, CW Gyrotron at 140 GHz for Wendelstein 7-X

G.Dammertz¹, S.Alberti², A.Arnold ^1,3, E.Borie¹, V.Erckmann⁴, G. Gantenbein, E.Giguet⁶,

R. Heidinger^1a, J.P. Hogge², S.Illy¹, W.Kasparek⁵, K.Koppenburg¹, M.Kuntze¹, H.P.Laqua⁴, G. LeCloarec⁶, F. Legrand⁶, W.Leonhardt¹, C.Lievin⁶, R. Magne⁷, G.Michel⁴, G.Müller⁵, G.Neffe¹, B.Piosczyk¹, M.Schmid¹, K. Schwoerer, M.Thumm^1,3, M.Q.Tran²

¹Forschungszentrum Karlsruhe, ¹Institut für Hochleistungsimpuls- und Mikrowellentechnik, ^1a Institut für Materialforschung I, Association EURATOM-FZK, Postfach 3640, D-76021 Karlsruhe, Germany

²Centre de Recherche en Physique des Plasmas, Association Euratom-Confédération Suisse, EPFL Ecublens, CH-1015 Lausanne, Suisse

³Universität Karlsruhe, Institut für Höchstfrequenztechnik und Elektronik,

Kaiserstr. 12, D-76128 Karlsruhe, Germany

⁴Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, Association EURATOM,

Wendelsteinstr. 1, D-17491 Greifswald, Germany

⁵Institut für Plasmaforschung, Universität Stuttgart, Pfaffenwaldring 31, D-70569 Stuttgart, Germany

⁶Thales Electron Devices, 2 Rue de Latécoère, F-78141 Vélizy-Villacoublay, France

⁷Association Euratom-CEA, Départment de Recherches sur la Fusion Controlée, F-13108,

Saint Paul Lez Durances, France

In a European collaboration, a 1 MW, 140 GHz, CW gyrotron is being developed for the
10-MW ECRH system of Wendelstein 7-X.

The prototype tube has been tested in long pulse operation. An output power of 0.97 MW has been achieved for 11.8 s (42% efficiency) and of 0.89 MW for 180 s. At a reduced electron beam current of 27-28 A, corresponding to 540 kW, a pulse length of 940 s could be obtained limited by pressure increase inside the tube.

The tube has been sent back to the factory for an expertise. An improved cooling for the internal ion getter pumps and a new cathode emitter ring will be installed. Experiments with the modified tube are expected in the nearest future.