A novel measurement of marginal Alfvén Eigenmode stability during high power auxiliary heating in JET

A novel measurement of marginal Alfvén Eigenmode stability during high power auxiliary heating in JET

A novel measurement of marginal Alfvén Eigenmode stability during high power auxiliary heating in JET 150 150 Mathew
UKAEA-CCFE-PR(21)36

A novel measurement of marginal Alfvén Eigenmode stability during high power auxiliary heating in JET

The interaction of Alfvén Eigenmodes (AEs) and energetic particles will determine the success of future tokamaks. In JET, eight in-vessel antennas were installed to actively probe stable AEs with frequencies ranging 25 – 250 kHz and toroidal mode numbers |n| < 20. During the 2019-2020 deuterium  campaign, almost 7500 resonances and their frequencies f0, net damping rates gamma < 0, and toroidal mode numbers were measured in almost 800 plasma discharges. From a statistical analysis of this database, continuum and radiative damping are inferred to increase with edge safety factor, edge magnetic shear, and when including non-ideal effects. Both stable AE observations and their associated damping rates are found to decrease with |n|. Active antenna excitation is also demonstrated to be ineffective in H-mode as opposed to L-mode, likely due to the increased edge density gradient. A novel measurement of marginal stability is reported for an edge-localized Ellipticity-induced AE in the presence of fast ion populations resulting from ICRH and NBI heating powers up to 25 MW. NOVA-K kinetic-MHD simulations show good agreement with experimental measurements of f0, gamma, and n, indicating the dominance of continuum and electron Landau damping in this case. Similar experimental and computational studies are planned for the recent hydrogen and ongoing tritium campaigns, in preparation for the upcoming DT campaign.

Collection:
Journals
Journal:
Nuclear Fusion
Publisher:
IOP (Institute of Physics)