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Simultaneous measurements of unstable and stable Alfvén eigenmodes in JET

Tinguely R.A.; Gonzalez-Martin J.; Puglia P.G.; Fil N.; Dowson S.; Porkolab M.; Kumar I.; Podesta M.; Baruzzo M.; Fasoli A.; Kazakov Y.O.; Nave M.F.F.; Nocente M.; Ongena J.; Stancar A.; Contributors J.E.T.

In this paper, we report the novel experimental observation of both unstable and stable toroidicity-induced Alfvén eigenmodes (TAEs) measured simultaneously in a JET tokamak plasma. The three-ion-heating scheme (D-DNBI-3He) is employed to accelerate deuterons to MeV energies, thereby destabilizing TAEs with toroidal mode numbers n = 3-5, each decreasing in mode amplitude. At the same time, the Alfvén eigenmode active diagnostic resonantly excites a stable n = 6 TAE with total normalized damping rate – 3/? 0 ? 1%-4%. Hybrid kinetic-MHD modeling with codes NOVA-K and MEGA both find eigenmodes with similar frequencies, mode structures, and radial locations as in experiment. NOVA-K demonstrates good agreement with the n = 3, 4, and 6 TAEs, matching the damping rate of the n = 6 mode within uncertainties and identifying radiative damping as the dominant contribution. Improved agreement is found with MEGA for all modes: the unstable n = 3-5 and stable n = 2, 6 modes, with the latter two stabilized by higher intrinsic damping and lower fast ion drive, respectively. While some discrepancies remain to be resolved, this unique validation effort gives us confidence in TAE stability predictions for future fusion devices.

ID 473538
DOI 10.1088/1741-4326/ac899e
PRODUCT TYPE Journal Article
LAST UPDATE 2022-11-17T16:17:55Z
EU PROJECT EUROfusion
TITLE Implementation of activities described in the Roadmap to Fusion during Horizon 2020 through a Joint programme of the members of the EUROfusion consortium
FOUNDING PROGRAM H2020
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