Mainz 2022 – scientific programme

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P: Fachverband Plasmaphysik

P 18: Helmholtz Graduate School HEPP IV

P 18.3: Talk

Thursday, March 31, 2022, 14:50–15:15, P-H12

Studies of propagating ICRF slow waves — •Felix Paulus, Volodymyr Bobkov, Helmut Faugel, Helmut Fünfgelder, Oleksii Girka, Roman Ochoukov, Hartmut Zohm, and ASDEX Upgrade Team — Max-Planck-Institut für Plasmaphysik Garching

Heating a plasma with ion cyclotron range of frequencies (ICRF) waves is an established technique in tokamaks. While the design of ICRF antennas aims to launch one solution of the plasma's dispersion relation (fast wave), the other is an unwanted by-product (slow wave). The slow wave propagates in low-density plasmas only and is usually confined to a small region in the scrape-off layer (SOL) or in the limiter shadow in present-day tokamaks. ICRF systems for future devices as ITER or DEMO will need to cope with a propagating slow wave in front of the antenna since a relatively large clearance is foreseen. Studying the slow wave is important because it modifies the antenna near-field and poses a mechanism for transporting plasma-wall interactions.

An approach to study the ICRF slow wave propagation in the ASDEX Upgrade (AUG) tokamak SOL is demonstrated. RAPLICASOL simulation indicates that in SOL relevant plasmas the slow wave manifests in so-called resonance cones. Experiments on the test stand IShTAR are presented where resonance cones were launched from an RF antenna and detected by probing the oscillation of the plasma potential. Based on these results, experiments on AUG are prepared. Preliminary results from these experiments with the slow wave launched from plasma-facing components of the antenna periphery are shown and compared to simulations.