Experiments on a 170 GHz Coaxial Cavity Gyrotron

B. Piosczyk^1a, A. Arnold², H. Budig^1a, G. Dammertz^1a, O. Dumbrajs³, R. Heidinger^1b, S. Illy^1a, J. Jin^1a,

G. Michel⁴, T. Rzesnicki^1a, M. Thumm^1a,2, X. Yang^1a

1Forschungszentrum Karlsruhe, Association EURATOM-FZK,

(a) IHM, ^(b) IMF I; Postfach 3640, D-76021 Karlsruhe, Germany,

2University Karlsruhe, IHE, D-76128 Karlsruhe, Germany

³Helsinki University of Technology, Association EURATOM-TEKES, FIN-02150 Espoo, Finland.

4Max-Planck-Institut fuer Plasmaphysik, Ass. EURATOM-IPP, D-17491 Greifswald, Germany

Within a development program performed as an ITER task at the Forschungszentrum Karlsruhe (FZK) the feasibility of manufacturing a multi-megawatt coaxial gyrotron operated in continuous wave (CW) has been investigated and information necessary for a technical design and industrial manufacturing has been obtained. Based on these results the development of a coaxial cavity gyrotron with an RF output power of 2 MW, CW at 170 GHz as could be used for ITER is in progress in cooperation between EURATOM Associations (CRPP Lausanne, FZK Karlsruhe and HUT Helsinki) together with European tube industry (Thales Electron Devices, Velizy, France).

In parallel to that work on a first industrial prototype tube, the previously used short pulse 165 GHz, TE_31,17 coaxial cavity gyrotron at FZK has been modified for operation at 170 GHz in the TE_34,19 cavity mode. The modified experimental gyrotron operates in the same mode as foreseen for the industrial prototype and uses a cavity with same dimensions. In addition, the gyrotron is equipped with an improved quasi-optical RF output system same as designed for the prototype. The experimental operation is planned to start within the next weeks. The investigations have two main goals:

(1) to verify experimentally the design of the main components of the industrial prototype by studying both the efficiency of RF generation and mode competition and the properties of the quasi-optical RF output system,

(2) to provide a high power, short pulse (~5-10 ms) test possibility for studying a prototype of the remotely steerable launcher of the upper ITER port plug for neoclassical tearing mode stabilization.

Results concerning as well the gyrotron operation and the conditions for the launcher test are expected and will be reported.