Hannover 2016 – scientific programme
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P: Fachverband Plasmaphysik
P 26: Poster Session-Plasma Diagnostics
P 26.9: Poster
Thursday, March 3, 2016, 16:30–19:00, Empore Lichthof
In-situ real-time monitoring of spurious modes in high power millimeter wave transmission lines using multi-hole couplers in miter bends — •W. Alexander Zach1, Walter Kasparek1, Carsten Lechte1, Burkhard Plaum1, Jörg Stober2, Francesco Monaco2, Harald Schütz2, Hiroshi Idei3, and Thomas Hirth1 — 1Institut für Grenzflächenverfahrenstechnik und Plasmatechnologie IGVP, Univ. Stuttgart, Pfaffenwaldring 31, D-70569 Stuttgart, Germany — 2Max-Planck-Institut für Plasmaphysik, EURATOM-IPP, D-85748 Garching, Germany — 3Research Institute for Applied Mechanics, Kyushu Univ., Kasuga, 816-8560, Japan
For Electron Cyclotron Resonance Heating (ECRH) in fusion experiments, millimeter waves have to be transmitted over large distances from gyrotrons to the plasma. In the case of e.g. ASDEX Upgrade, millimeter waves with up to 1 MW of power at 140 GHz are transmitted via waveguides. Because of the high power, oversized corrugated circular waveguides are used. However, these are sensitive to alignment errors, which lead to the excitation of higher order spurious modes besides the favored hybrid mode HE11. An alignment analysis would require a complete 2D field scan, which is not possible for high powers.
As an alternative, hole-array-couplers, placed in the cross section of the transmission line at a miter bend location, allow for an in-situ measurement of the power of modes, that are predominantly excited due to misalignment. Complex signals can either be processed independently or via a hard-wired interferometric setup. Simulations and experimental results are discussed.