Abstract Details
Abstracts
Author: Joseph R Jepson
Requested Type: Consider for Invited
Submitted: 2026-02-28 23:32:53
Co-authors: J. R. Jepson, S. A. Sabbagh, J. D. Riquezes, E. C. Howell, G. Bustos-Ramirez, Hankyu Lee, G. Tillinghast, M. Tobin, V. Zamkovska, C. J. Ham, S. Blackmore, J. Kim, Y. S. Park
Contact Info:
Columbia University
100 Stellerator Road
Princeton, NJ 08540
United States
Abstract Text:
As the fusion community seeks to advance towards a net-energy producing reactor, disruption prediction and avoidance remains of paramount importance to tokamaks. Many disruptions in current experiments are caused when large 3D resistive MHD modes grow in the plasma, resulting in loss of plasma control. Often, when these 3D modes grow to large enough amplitude, coupling to eddy currents in the wall or to intrinsic error fields in the magnetic configuration results in a slowdown of the plasma rotation – further amplifying mode growth. Controlling these MHD modes and keeping them from locking could break the aforementioned positive feedback loop. One promising method for mode control in tokamaks is that of neoclassical tearing mode (NTM) pseudo-entrainment [1], where a very slowly rotating (10s to 100s of Hz) external magnetic field perturbation is applied to keep an otherwise-locking mode in the plasma from locking. The pseudo-entrainment creates a new torque balance of the the mode rotating at a far higher speed (kHz-level). This is in contrast to classical entrainment which seeks to entrain a mode at the same (or similar) rotation speed as the externally applied perturbation [2]. The physics of NTM pseudo-entrainment is not fully understood. In this work, we utilize NIMROD to explore the physics of NTM pseudo-entrainment in tokamak plasmas (including spherical tokamak plasmas). In particular, we analyze how (and why) a magnetic perturbation with slow – but non-zero – rotation might change the underlying configuration, and how such a change can prove beneficial toward preventing mode locking.
[1] KSTAR MP2021-04-04-026 Y. S. Park, S.A. Sabbagh, et al.
[2] F.A. Volpe et al., “Advanced techniques for neoclassical tearing mode control in DIII-D”, Phys. Plasmas 60, 102502 (2009)
Characterization: 1.0
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