SMuK 2021 – scientific programme
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P: Fachverband Plasmaphysik
P 15: Magnetic Confinement V & Helmholtz Graduate School V
P 15.4: Talk
Thursday, September 2, 2021, 17:50–18:15, H5
Plasma electron acceleration up to 100 keV in the TJ-K stellarator — •Alf Köhn-Seemann1, Gregor Birkenmeier2,3, Eberhard Holzhauer1, Mirko Ramisch1, Gabriel Sichardt1, and Ulrich Stroth2,3 — 1IGVP, University of Stuttgart — 2Max Planck Institute for Plasma Physics, Garching — 3Physics Department E28, TUM, Garching
In conventional microwave heating scenarios, the injected microwaves' frequency must be equal to or higher than the electron cyclotron frequency (ECF) to transfer their energy to the plasma. Here, we describe in contrast an operational regime at the stellarator TJ-K where the heating occurs well below the ECF, but still above the lower-hybrid frequency: energy is deposited at the so-called O-resonance. A population of high-energy electrons observed in the scenario is attributed to strong wave electric fields at this resonance. Simple physics considerations estimating the energy gain during a half-cycle of the wave electric field have been used to describe this acceleration scheme for plasma electrons. The model has been successfully compared with measurements using a pulse-height analyzer allowing to determine the fast electrons' energy.