Numerical simulations of global Alfvén eigenmodes excitation and stabilization in NSTX-U

Belova, E. V.; Fredrickson, E. D.; Lestz, J. B.; Crocker, N. A.

doi:10.1063/1.5116357

Numerical simulations of global Alfvén eigenmodes excitation and stabilization in NSTX-U

Journal Article · Thu Sep 12 00:00:00 EDT 2019 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.5116357· OSTI ID:1561973

^[1]; Fredrickson, E. D. ^[1]; ^[1]; ^[2]

Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
Department of Physics &, Astronomy, University of California, Los Angeles, California 90095, USA

Three-dimensional nonlinear simulations of Alfvén eigenmodes in the subcyclotron frequency range demonstrate a robust physical stabilizing mechanism via modest off-axis beam injection, in agreement with experimental observations from the National Spherical Torus Experiment (NSTX-U). Experimental results from NSTX-U have demonstrated that neutral beam injection from the new beam sources with large tangency radii deposits beam ions with large pitch, which can very effectively stabilize all unstable Global Alfvén Eigenmodes (GAEs). Beam-driven GAEs have been linked to enhanced electron transport in NSTX, and the ability to control these modes will have significant implications for NSTX-U, ITER, and other fusion devices where super-Alfvénic fast ions might be present. Nonlinear simulations using the HYM code have been performed to study the excitation and stabilization of GAEs in the NSTX-U right before and shortly after the additional off-axis beam injection. The simulations reproduce the experimental finding, namely, it is shown that off-axis neutral beam injection reliably and strongly suppresses all unstable GAEs. Before additional beam injection, the simulations show unstable counter-rotating GAEs with toroidal mode numbers and frequencies that match the experimentally determined modes. Additional off-axis beam injection has been modeled by adding beam ions with large pitch and varying density. The complete stabilization occurs at less than 7% of the total beam ion inventory. New analytical theory of GAE (de)stabilization has also been derived, indicating a different interpretation for the GAE stabilization mechanism compared to previous publications.

View Accepted Manuscript (DOE)

Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE

Contributing Organization:: NSTX-U Team

Grant/Contract Number:: SC0011810; AC02-09CH11466

OSTI ID:: 1561973

Alternate ID(s):: OSTI ID: 1561389

Journal Information:: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 9 Vol. 26; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Analytic stability boundaries for compressional and global Alfvén eigenmodes driven by fast ions. I. Interaction via ordinary and anomalous cyclotron resonances Lestz, J. B.; Gorelenkov, N. N.; Belova, E. V. Physics of Plasmas, Vol. 27, Issue 2 https://doi.org/10.1063/1.5127551	journal	February 2020
Analytic stability boundaries for compressional and global Alfvén eigenmodes driven by fast ions. II. Interaction via Landau resonance Lestz, J. B.; Gorelenkov, N. N.; Belova, E. V. Physics of Plasmas, Vol. 27, Issue 2 https://doi.org/10.1063/1.5127552	journal	February 2020
Analytic stability boundaries for compressional and global Alfvén eigenmodes driven by fast ions. II. Interaction via Landau resonance Lestz, J. B.; Gorelenkov, N. N.; Belova, E. V. arXiv https://doi.org/10.48550/arxiv.1909.05465	text	January 2019

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