Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Plasma Physics
Monday–Friday, October 7–11, 2024; Atlanta, Georgia
Session CO06: MFE:Stellarators, Helical Systems, and 3D Effects
2:00 PM–5:00 PM,
Monday, October 7, 2024
Hyatt Regency
Room: Hanover DE
Chair: Diane Demers, Xantho Technologies, LLC
Abstract: CO06.00012 : Wall Touching Kink Mode and toroidal asymmetry in current spike measurements in JET disruptions*
4:12 PM–4:24 PM
Presenter:
Sergei N Gerasimov
(UKAEA Culham Campus)
Authors:
Sergei N Gerasimov
(UKAEA Culham Campus)
Leonid Zakharov
(LiWFusion; Department of Physics, University of Helsinki)
Calin V Atanasiu
(National Institute for Laser, Plasma and Radiation)
Collaboration:
JET Contributors and the EUROfusion Tokamak Exploitation Team
The tokamak plasma exists primarily due to stabilization by surface currents, which act as a natural feedback mechanism. At the leading edge of the plasma surface displacement, their direction is always opposite to the bulk plasma current. Negative surface plasma currents enter the wall at a specific toroidal location and exit at another location on the same magnetic field line as the entrance. The circuit for these so-called Hiro currents makes several turns around the tokamak axis. It includes a large contact resistance between the plasma and the wall, causing a negative voltage spike on full flux loops. Due to this extra resistance, Hiro currents decay faster than their positive counterparts, excited by the same inductive effect at the plasma edge, leading to a measurable total plasma current spike.
In cross-sections with Hiro currents already in the wall, the plasma current measurements show an enhanced current spike. This enhancement cannot exceed 1/q 1/m, where m is the poloidal mode number of the dominant Fourier harmonic of WTKM. This explains the observed asymmetry in the plasma current spikes on JET.
*This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 - EUROfusion) and from the EPSRC [grant number EP/W006839/1]. Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them. The work was also supported by the U.S. DoE grant DE-SC0025274.
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