1 MW, 140 GHz, CW gyrotron for Wendelstein 7-X

A continuous wave, 1 MW, 140 GHz gyrotron oscillator has been designed and constructed as a joint collaboration between FZK Karlsruhe, CRPP Lausanne, IPF Stuttgart, CEA Cadarache and TTE Velizy for the 10 MW ECRH system of the new stellarator plasma physics experiment, Wendelstein 7-X, at IPP Greifswald, Germany. The tube is equipped with a diode MIG gun, an improved beam tunnel, a high-mode purity low-ohmic loss cavity, an optimized nonlinear up-taper, a highly efficient internal quasioptical mode converter, a single stage depressed collector for energy recovery and a large-aperture, edge-cooled, single disk CVD-diamond window and will be operated in the TE/sub 28.8/ mode. The gyrotron design and the teststand at the Forschungszentrum Karlsruhe are described; first experimental results for short pulse operation are presented.