Bremen 2017 – scientific programme
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P: Fachverband Plasmaphysik
P 6: Helmholtz Graduate School I
P 6.11: Poster
Monday, March 13, 2017, 16:30–18:30, HS Foyer
An approach to an electronic stability control for gyrotrons — •Fabian Wilde1, Stefan Marsen1, Ioannis Pagonakis2, Konstantinos Avramidis2, Torsten Stange1, Heinrich Laqua1, and John Jelonnek2 — 1Max Planck Institute for Plasma Physics (IPP), Wendelsteinstr. 1, D-17489 Greifswald, Germany — 2Institute for Pulsed Power and Microwave Technology (IHM), Karlsruhe Institute of Technology (KIT), Kaiserstr. 12, D-76131 Karlsruhe, Germany
Wendelstein 7-X (W7-X) uses electron cyclotron resonance heating (ECRH) by 140 GHz high-power microwave sources (gyrotrons) as primary heating method. Therefore a fast, electronic stability control for gyrotrons, allowing operation at highest possible output powers with maximum efficiency, is desireable. Such a control unit needs to implement a stabilization scheme using a reliable precursor for mode loss and a fast, automated mode recovery, if it fails.
Consequently shot spectrograms of the stray radiation were examined to identify a suitable precursor. A preliminary candidate appeared above 142 GHz, hence a D-band RF diode together with a high-pass filter was used to quantify the parasitic activity. A preliminary statistical analysis of 3000 shots yields a reasonable distribution for the probability of failure, nevertheless, a better precursor could be obtained using a 140 GHz notch filter to take into account the azimuthal neighbour mode. First experiments with a FPGA-based prototype, implementing the automated mode recovery, will be conducted soon. Multi-mode simulations, taking beam charge neutralization into account, will be used to describe a physical gyrotron reliability model.