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Global Alfvén eigenmode scaling and suppression: experiment and theory

Journal Article · · Nuclear Fusion
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  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Univ. of California, Los Angeles, CA (United States)
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The spherical tokamak NSTX has been upgraded to include a second neutral beam line, with three independent beam sources, and to be capable of higher toroidal fields and longer duration plasmas [Ono, et al., Nucl. Fusion 55 (2015) 073007]. In this paper we describe some of the initial observations of the affect that the higher field and the modified fast-ion distributions have had on the nature of the global Alfvén eigenmodes (GAE). We also report that the GAE excited through a Doppler-shifted ion cyclotron resonance (DCR) were suppressed in a large number of shots with the injection of a small amount of high pitch (V||/V) fast ions, consistent with the predictions of an analytic theory [Gorelenkov, et al., Nucl. Fusion 43 (2003) 228]. We show that the experimental scaling of the GAE frequency and toroidal mode numbers with toroidal field is qualitatively consistent with the predictions of the analytic theory, providing validation for the DCR model. The observed suppression of GAE has also been reproduced in simulations with the hybrid ideal stability code HYM [Belova, et al., Phys. Plasmas 24 (2017), 042505].

Research Organization:
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
Sponsoring Organization:
USDOE
Contributing Organization:
the NSTX-U team
Grant/Contract Number:
AC02-09CH11466
OSTI ID:
1463512
Journal Information:
Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 8 Vol. 58; ISSN 0029-5515
Publisher:
IOP ScienceCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (2)

Numerical simulations of global Alfvén eigenmodes excitation and stabilization in NSTX-U journal September 2019
Analytic stability boundaries for compressional and global Alfvén eigenmodes driven by fast ions. I. Interaction via ordinary and anomalous cyclotron resonances journal February 2020

Figures / Tables (14)

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