Hannover 2020 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 10: Poster Session 2
P 10.11: Poster
Dienstag, 10. März 2020, 16:30–18:30, Empore Lichthof
Self-consistent 2D fluid model for optimizing RF coupling at NNBI ion sources — •Dominikus Zielke1,2, Stiliyan Lishev3, Stefan Briefi1,2, and Ursel Fantz1,2 — 1Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany — 2AG Experimentelle Plasmaphysik, Universität Augsburg, 86135 Augsburg, Germany — 3Faculty of Physics, Sofia University, 1164 Sofia, Bulgaria
In Negative-ion based Neutral Beam Injection systems (NNBI) for fusion, a hydrogen plasma is generated via inductive RF coupling at a frequency of 1 MHz inside the ion source in cylindrical vessels, called drivers. At low gas pressures of 0.3 Pa, electron densities and temperatures of 1018 m−3 and 10 eV are reached. Only a fraction η of the generator power of up to 100 kW per driver is absorbed by the plasma, the rest is lost via eddy currents in the RF network, the internal Faraday screen and the surrounding steel structure. Since at 100 kW, the RF components work close to their technological limits, it is desirable to use lower generator powers while increasing η.
To optimize the RF coupling with respect to e.g. RF frequency or geometry, a 2D cylindrically symmetric multi-species fluid model is used, which describes the coupling between the RF fields and the electrons in the stochastic heating regime self-consistently.
The model is successfully validated with electrical and Langmuir probe measurements from the BATMAN Upgrade ion source testbed, where η is measured to be around 70-80%. The model is then utilized to study the impact of the distances between RF coil windings, coil and discharge, Faraday screen and surrounding steel structure on η.