ECRH-Development at Forschungszentrum Karlsruhe

G. Dammertz^1a, R. Heidinger^1b, K. Koppenburg^1a, B. Piosczyk^1a, M. Thumm^1a,2

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

²Universität Karlsruhe, Institut für Höchstfrequenztechnik und Elektronik,

Kaiserstr. 12, D-76128 Karlsruhe, Germany

e-mail: guenter.dammertz@ihm.fzk.de; phone: (+49) 7247-82 41 60; fax: (+49) 7247 / 82 4874

At Forschungszentrum Karlsruhe, gyrotrons, transmission lines and antennas for electron-cyclotron-resonance-heating and current-drive are investigated in close collaboration with other European Fusion Associations.

a) The development, installation, commissioning and test of the complete 10 MW, CW operated ECH system for the Stellarator Wendelstein 7-X at IPP Greifswald (in collaboration with the EPFL Lausanne and IPF Stuttgart) will be described and the present status will be given. The prototype gyrotron yielded an output power of 890 kW for three minutes (limited by the available power supply) and an output power of 539 kW for 939 s (limited by the pressure increase inside the gyrotron). The specified output power and pulse length has not been achieved completely. The reasons are understood and the development phase has been finished. In order to overcome these limitations the design has been modified slightly. The series gyrotrons and the superconducting magnets have been ordered.

b) The fabrication phase of an industrial CW operated coaxial cavity gyrotron at 170 GHz has started recently in cooperation between European research centers (FZK, CRPP Lausanne, HUT Helsinki) and European tube industry (Thales Electron Devices, Vélizy). To verify experimentally the design of critical components the present coaxial cavity 165 GHz gyrotron available at FZK has been redesigned and modified for operation at 170 GHz. The most recent experiments will be reported.

c) Multifrequency step-tunable gyrotrons with an output power of 1 MW are needed for controlling plasma instabilities in fusion tokamaks (as in ASDEX Upgrade). Within a collaboration between FZK and IAP (Nizhny Novgorod, Russia), a short-pulse gyrotron is developed at FZK in order to investigate the behaviour of components, especially a quasi-optical mode converter and a Brewster windows. The gyrotron operates in the TE_22,8 mode at 140 GHz, in the TE_17,6 mode at 105 GHz and some others in between. The latest design results of the Brewster window and experimental results of the cold measurements will be presented.