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Title: Fast-ion transport by Alfvén eigenmodes above a critical gradient threshold

Authors:
 [1];  [2]; ORCiD logo [3];  [3]; ORCiD logo [2];  [2]; ORCiD logo [1];  [2];  [3];  [1]
  1. University of California Irvine, Irvine, California 92697, USA
  2. General Atomics, San Diego, California 92186, USA
  3. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1349370
Grant/Contract Number:
FC02-04ER54698
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 5; Related Information: CHORUS Timestamp: 2018-02-14 23:58:00; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics
Country of Publication:
United States
Language:
English

Citation Formats

Heidbrink, W. W., Collins, C. S., Podestà, M., Kramer, G. J., Pace, D. C., Petty, C. C., Stagner, L., Van Zeeland, M. A., White, R. B., and Zhu, Y. B. Fast-ion transport by Alfvén eigenmodes above a critical gradient threshold. United States: N. p., 2017. Web. doi:10.1063/1.4977535.
Heidbrink, W. W., Collins, C. S., Podestà, M., Kramer, G. J., Pace, D. C., Petty, C. C., Stagner, L., Van Zeeland, M. A., White, R. B., & Zhu, Y. B. Fast-ion transport by Alfvén eigenmodes above a critical gradient threshold. United States. doi:10.1063/1.4977535.
Heidbrink, W. W., Collins, C. S., Podestà, M., Kramer, G. J., Pace, D. C., Petty, C. C., Stagner, L., Van Zeeland, M. A., White, R. B., and Zhu, Y. B. Mon . "Fast-ion transport by Alfvén eigenmodes above a critical gradient threshold". United States. doi:10.1063/1.4977535.
@article{osti_1349370,
title = {Fast-ion transport by Alfvén eigenmodes above a critical gradient threshold},
author = {Heidbrink, W. W. and Collins, C. S. and Podestà, M. and Kramer, G. J. and Pace, D. C. and Petty, C. C. and Stagner, L. and Van Zeeland, M. A. and White, R. B. and Zhu, Y. B.},
abstractNote = {},
doi = {10.1063/1.4977535},
journal = {Physics of Plasmas},
number = 5,
volume = 24,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2017},
month = {Mon May 01 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1063/1.4977535

Citation Metrics:
Cited by: 4works
Citation information provided by
Web of Science

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  • Experiments in the DIII-D tokamak show that many overlapping small-amplitude Alfv en eigenmodes (AEs) cause fast-ion transport to sharply increase above a critical threshold, leading to fast-ion density profile resilience and reduced fusion performance. The threshold is above the AE linear stability limit and varies between diagnostics that are sensitive to different parts of fast-ion phase-space. A comparison with theoretical analysis using the nova and orbit codes shows that, for the neutral particle diagnostic, the threshold corresponds to the onset of stochastic particle orbits due to wave-particle resonances with AEs in the measured region of phase space. We manipulated themore » bulk fast-ion distribution and instability behavior through variations in beam deposition geometry, and no significant differences in the onset threshold outside of measurement uncertainties were found, in agreement with the theoretical stochastic threshold analysis. Simulations using the `kick model' produce beam ion density gradients consistent with the empirically measured radial critical gradient and highlight the importance of including the energy and pitch dependence of the fast-ion distribution function in critical gradient models. The addition of electron cyclotron heating changes the types of AEs present in the experiment, comparatively increasing the measured fast-ion density and radial gradient. Our studies provide the basis for understanding how to avoid AE transport that can undesirably redistribute current and cause fast-ion losses, and the measurements are being used to validate AE-induced transport models that use the critical gradient paradigm, giving greater confidence when applied to ITER.« less
    Cited by 1
  • A new non-linear feature has been observed in fast-ion loss from tokamak plasmas in the form of oscillations at the sum, difference and second harmonic frequencies of two independent Alfvén eigenmodes (AEs). Full orbit calculations and analytic theory indicate this non-linearity is due to coupling of fast-ion orbital response as it passes through each AE — a change in wave-particle phase k • r by one mode alters the force exerted by the next. Furthermore, the loss measurement is of barely confined, non-resonant particles, while similar non-linear interactions can occur between well-confined particles and multiple AEs leading to enhanced fast-ionmore » transport.« less