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Abstract

For the development of a 1 MW, 140 GHz gyrotron for CW operation, which will be installed at the stellarator facility Wendelstein 7-X at IPP Greifswald, collaboration between different European research institutes and an industrial company has been established. In order to prove the proper functioning of the millimetre wave components installed in the gyrotron these components should be cold tested, preferably before installation. However, this was not possible. Therefore, two units of the quasi-optical mode converter and the cavity were fabricated with identical geometry, one of those being used for measurements on the low power test device. To perform these cold tests for tapers and mode converters, the gyrotron cavity output mode has to be simulated. This means that a high order rotating mode must be generated at low power.

This can be achieved by means of a mode generator consisting of two mirrors and a coaxial cavity with a perforated outer wall. Before applying the mode generator to the components, its proper behaviour and the accurate alignment of the system must be verified either by radiation pattern measurements or k-spectrometer measurements. As the coupling through the holes of the k-spectrometer is extremely low, a special vector network analyser with a dynamic range of at least 100 dB had to be developed.

This has been achieved by integration of a phase locked backward-wave oscillator with a line width of 100 Hz and an output power of 10 mW. A non-destructive measurement of the resonance frequency and the quality factor of the cavity does not seem possible. le.

Additional information

Authors: DAMMERTZ G, Forschungszentrum Karlsruhe GmbH (DE);ALBERTI S, CRPP, Ecole Polytechnique Federale de Lausanne, Lausanne (CH);ARNOLD A, Forschungszentrum Karlsruhe GmbH (DE) and Universitaet Karlsruhe, Institut fur Hochstfrequenztechnik und Elektronik, Karlsruhe (DE);THUMM M, Forschungszentrum Karlsruhe GmbH (DE) and Universitaet Karlsruhe, Institut fur Hochstfrequenztechnik und Elektronik, Karlsruhe (DE);GIGUET E, Thomson Tubes Electroniques, velizy-Villacoublay (FR);LEGOFF Y, Thomson Tubes Electroniques, velizy-Villacoublay (FR)
Bibliographic Reference: An article published in: Fusion Engineering and Design, Vol.53, (2001), pp.561-569
Record Number: 200113873 / Last updated on: 2001-10-09
Category: PUBLICATION
Original language: en
Available languages: en