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P: Fachverband Plasmaphysik

P 16: Poster Session Plasma Physics

P 16.4: Poster

Donnerstag, 19. März 2026, 13:45–15:45, Redoutensaal

Beat wave generation in the ion cyclotron frequency range by high power microwaves and how to measure them — •Niklas Simon Polei, Laurent Krier, Heinrich Peter Laqua, Dmitry Moseev, Sergiy Ponomarenko, Torsten Stange, and W7-X Team — Max-Planck-Institut für Plasmaphysik, Greifswald, Germany

The overlap of two waves will create a third wave beating with the frequency difference (Δ f) of the two original waves. For the beat wave generation in the ion cyclotron frequency (ICF) range two gyrotrons of the electron cyclotron resonance heating system of Wendelstein 7-X (W7-X) are used. The gyrotrons are frequency stabilized by a phase locked loop, so that they are oscillating by 100kHz at most [1]. The Δ f is set to the ICF in the overlap region, typically 35MHz to 37MHz.

The microwave beams can be either overlapped in the resonance region [2] or before the resonance region. Different processes are then transferring energy to the ions. In the latter case the overlap creates a strong electric field gradient, this results in an electron density wave created by the ponderomotive force. If the k-vector of the electron wave is chosen appropriately it can couple to the ion Bernstein waves.

So far only the ICRH antenna of W7-X was used in measurements. However, no waves or ion heating could be observed. Therefore, it is planned to use the collective Thomson scattering (CTS) system and the fast ion loss detector (FILD) to detect ion heating or fast ions.

[1] L. Krier, et al. doi: 10.1109/IRMMW-THz50926.2021.9566847
[2] H.P. Laqua, et al. 2018 Nucl. Fusion 58 104003

Keywords: gyrotron; beat wave; ECRH; W7-X