Advanced High Power Gyrotron for W7-X

 

G. Dammertz1, S. Alberti5, E. Borie1, V. Erckmann6, E. Giguet3, S. Illy1,
K. Koppenburg1, M. Kuntze1, H.P. Laqua6,Y. Le Goff3, W. Kasparek4,
W. Leonhardt1, G. Michel6, G. Müller4, B. Piosczyk1, M. Schmid1,
M. Thumm1,2, M.Q. Tran5

 

 

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

2Universität Karlsruhe, Institut für Höchstfrequenztechnik und Elektronik,

Kaiserstr. 12, D-76128 Karlsruhe, Germany

3Thales Electron Devices, 2 Rue de Latécoère, F-78141 Vélizy-Villacoublay, France

4Institut für Plasmaforschung, Universität Stuttgart, Pfaffenwaldring 31, D-70569 Stuttgart, Germany

5Centre de Recherche en Physique des Plasmas, Association EURATOM-Confédération Suisse, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland

6Max-Planck-Institut für Plasmaphysik (IPP), Association EURATOM, 17491 Greifswald, Germany

 

A 1 MW, 140 GHz gyrotron with diamond window for continuous wave operation and with a single-stage depressed collector has been designed and constructed in collaboration with several EURATOM Associations. It operates in the TE28,8 cavity mode and provides a linearly polarized TEM0,0 output beam. The gyrotron consists of a magnetron injection gun, an improved cavity, an optimized non-linear up-taper and an improved launcher.

RF power measurements at short pulse lengths (10 ms) gave 1.1 MW output power at the design values of 80 kV beam voltage and 40 A beam current. The depressed collector could be operated up to 33 kV, which gives an efficiency of 49% and an improvement factor of 1.7. At 880 kW output power a pulse length of 7.8 s could be achieved with an efficiency of 43%. The pulse length was limited due to the pressure increase inside the tube. Conditioning of the tube at this power level was not possible due to arcing in the load. With reduced power levels a pulse length of 45 s at 750 kW output power (limited by arcing in the load) and of 150 s at 450 kW has been achieved. The latest results and effects of the diamond window disk will be presented.