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Title: Global Alfvén eigenmode scaling and suppression: experiment and theory

Abstract

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].

Authors:
 [1];  [1];  [1]; ORCiD logo [1];  [1]; ORCiD logo [2];  [1];  [1]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Univ. of California, Los Angeles, CA (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
Contributing Org.:
the NSTX-U team
OSTI Identifier:
1463512
Grant/Contract Number:  
AC02-09CH11466; DESC-SC0011810
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 58; Journal Issue: 8; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Fredrickson, E. D., Belova, E. V., Gorelenkov, N. N., Podesta, M., Bell, R. E., Crocker, N. A., Diallo, A., and LeBlanc, B. P. Global Alfvén eigenmode scaling and suppression: experiment and theory. United States: N. p., 2018. Web. doi:10.1088/1741-4326/aac64c.
Fredrickson, E. D., Belova, E. V., Gorelenkov, N. N., Podesta, M., Bell, R. E., Crocker, N. A., Diallo, A., & LeBlanc, B. P. Global Alfvén eigenmode scaling and suppression: experiment and theory. United States. doi:10.1088/1741-4326/aac64c.
Fredrickson, E. D., Belova, E. V., Gorelenkov, N. N., Podesta, M., Bell, R. E., Crocker, N. A., Diallo, A., and LeBlanc, B. P. Mon . "Global Alfvén eigenmode scaling and suppression: experiment and theory". United States. doi:10.1088/1741-4326/aac64c. https://www.osti.gov/servlets/purl/1463512.
@article{osti_1463512,
title = {Global Alfvén eigenmode scaling and suppression: experiment and theory},
author = {Fredrickson, E. D. and Belova, E. V. and Gorelenkov, N. N. and Podesta, M. and Bell, R. E. and Crocker, N. A. and Diallo, A. and LeBlanc, B. P.},
abstractNote = {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].},
doi = {10.1088/1741-4326/aac64c},
journal = {Nuclear Fusion},
number = 8,
volume = 58,
place = {United States},
year = {2018},
month = {5}
}

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Figures / Tables:

Fig. 1. Fig. 1.: a) spectrogram of magnetic sensor signal, b) plasma current, c) injected power from each of the three neutral beam sources.

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    Works referencing / citing this record:

    Numerical simulations of global Alfvén eigenmodes excitation and stabilization in NSTX-U
    journal, September 2019

    • Belova, E. V.; Fredrickson, E. D.; Lestz, J. B.
    • Physics of Plasmas, Vol. 26, Issue 9
    • DOI: 10.1063/1.5116357