skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Phase-space dependent critical gradient behavior of fast-ion transport due to Alfvén eigenmodes

Abstract

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 the 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 themore » 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

Authors:
 [1];  [2];  [3];  [3];  [3];  [1];  [1];  [2];  [1];  [2]
  1. General Atomics, San Diego, CA (United States)
  2. Univ. of California, Irvine, CA (United States)
  3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Contributing Org.:
The DIII-D Team
OSTI Identifier:
1374553
Grant/Contract Number:  
FC02-04ER54698; FG03-94ER54271; AC02- 09CH11466
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; 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; energetic particles; fast-ion transport; Alfven eigenmodes; critical gradient

Citation Formats

Collins, C. S., Heidbrink, W. W., Podestà, M., White, R. B., Kramer, G. J., Pace, D. C., Petty, C. C., Stagner, L., Van Zeeland, M. A., and Zhu, Y. B. Phase-space dependent critical gradient behavior of fast-ion transport due to Alfvén eigenmodes. United States: N. p., 2017. Web. doi:10.1088/1741-4326/aa720c.
Collins, C. S., Heidbrink, W. W., Podestà, M., White, R. B., Kramer, G. J., Pace, D. C., Petty, C. C., Stagner, L., Van Zeeland, M. A., & Zhu, Y. B. Phase-space dependent critical gradient behavior of fast-ion transport due to Alfvén eigenmodes. United States. doi:10.1088/1741-4326/aa720c.
Collins, C. S., Heidbrink, W. W., Podestà, M., White, R. B., Kramer, G. J., Pace, D. C., Petty, C. C., Stagner, L., Van Zeeland, M. A., and Zhu, Y. B. Fri . "Phase-space dependent critical gradient behavior of fast-ion transport due to Alfvén eigenmodes". United States. doi:10.1088/1741-4326/aa720c. https://www.osti.gov/servlets/purl/1374553.
@article{osti_1374553,
title = {Phase-space dependent critical gradient behavior of fast-ion transport due to Alfvén eigenmodes},
author = {Collins, C. S. and Heidbrink, W. W. and Podestà, M. and White, R. B. and Kramer, G. J. and Pace, D. C. and Petty, C. C. and Stagner, L. and Van Zeeland, M. A. and Zhu, Y. B.},
abstractNote = {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 the 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.},
doi = {10.1088/1741-4326/aa720c},
journal = {Nuclear Fusion},
number = 8,
volume = 57,
place = {United States},
year = {2017},
month = {6}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 5 works
Citation information provided by
Web of Science

Save / Share:

Works referenced in this record:

Basic physics of Alfvén instabilities driven by energetic particles in toroidally confined plasmas
journal, May 2008


Energetic particle physics in fusion research in preparation for burning plasma experiments
journal, November 2014


The tokamak Monte Carlo fast ion module NUBEAM in the National Transport Code Collaboration library
journal, June 2004

  • Pankin, Alexei; McCune, Douglas; Andre, Robert
  • Computer Physics Communications, Vol. 159, Issue 3
  • DOI: 10.1016/j.cpc.2003.11.002

Fast-ion transport in qmin>2, high- β steady-state scenarios on DIII-Da)
journal, May 2015

  • Holcomb, C. T.; Heidbrink, W. W.; Ferron, J. R.
  • Physics of Plasmas, Vol. 22, Issue 5
  • DOI: 10.1063/1.4921152

Confinement degradation by Alfvén-eigenmode induced fast-ion transport in steady-state scenario discharges
journal, August 2014


Alpha‐particle losses from toroidicity‐induced Alfvén eigenmodes. Part II: Monte Carlo simulations and anomalous alpha‐loss processes
journal, June 1992

  • Sigmar, D. J.; Hsu, C. T.; White, R.
  • Physics of Fluids B: Plasma Physics, Vol. 4, Issue 6
  • DOI: 10.1063/1.860061

Line broadened quasi-linear burst model [fusion plasma]
journal, December 1995


Double-resonant fast particle-wave interaction
journal, September 2012


Loss of energetic beam ions during TAE instabilities
journal, May 1993


Toroidal Alfvén eigenmode‐induced ripple trapping
journal, August 1995

  • White, R. B.; Fredrickson, E.; Darrow, D.
  • Physics of Plasmas, Vol. 2, Issue 8
  • DOI: 10.1063/1.871452

Observations of neutral beam and ICRF tail ion losses due to Alfven modes in TFTR
journal, July 1997


Observation and modelling of fast ion loss in JET and ASDEX Upgrade
journal, September 2006


Anomalous Flattening of the Fast-Ion Profile during Alfvén-Eigenmode Activity
journal, December 2007


Confinement degradation and transport of energetic ions due to Alfvén eigenmodes in JT-60U weak shear plasmas
journal, July 2007


Beam distribution modification by Alfvén modes
journal, May 2010

  • White, R. B.; Gorelenkov, N.; Heidbrink, W. W.
  • Physics of Plasmas, Vol. 17, Issue 5
  • DOI: 10.1063/1.3327208

NTM induced fast ion losses in ASDEX Upgrade
journal, June 2007


MHD instabilities and their effects on plasma confinement in Large Helical Device plasmas
journal, January 2004


A study on the TAE-induced fast-ion loss process in LHD
journal, April 2013


Experimental studies on fast-ion transport by Alfvén wave avalanches on the National Spherical Torus Experiment
journal, May 2009

  • Podestà, M.; Heidbrink, W. W.; Liu, D.
  • Physics of Plasmas, Vol. 16, Issue 5
  • DOI: 10.1063/1.3080724

Stochastic orbit loss of neutral beam ions from NSTX due to toroidal Alfvén eigenmode avalanches
journal, December 2012


Measurements and modelling of fast-ion redistribution due to resonant MHD instabilities in MAST
journal, November 2015


Fast particle behaviour in the Globus-M spherical tokamak
journal, March 2015


Observation of Critical-Gradient Behavior in Alfvén-Eigenmode-Induced Fast-Ion Transport
journal, February 2016


Fast-ion transport by Alfvén eigenmodes above a critical gradient threshold
journal, May 2017

  • Heidbrink, W. W.; Collins, C. S.; Podestà, M.
  • Physics of Plasmas, Vol. 24, Issue 5
  • DOI: 10.1063/1.4977535

1.5D quasilinear model and its application on beams interacting with Alfvén eigenmodes in DIII-D
journal, September 2012

  • Ghantous, K.; Gorelenkov, N. N.; Berk, H. L.
  • Physics of Plasmas, Vol. 19, Issue 9
  • DOI: 10.1063/1.4752011

Prediction of the fusion alpha density profile in ITER from local marginal stability to Alfvén eigenmodes
journal, October 2014


Electron cyclotron emission radiometer upgrade on the DIII-D tokamak
journal, March 2003

  • Austin, M. E.; Lohr, J.
  • Review of Scientific Instruments, Vol. 74, Issue 3
  • DOI: 10.1063/1.1530387

Electron cyclotron heating can drastically alter reversed shear Alfvén eigenmode activity in DIII-D through finite pressure effects
journal, July 2016


Compact solid-state neutral particle analyzer in current mode
journal, October 2012

  • Zhu, Y. B.; Bortolon, A.; Heidbrink, W. W.
  • Review of Scientific Instruments, Vol. 83, Issue 10
  • DOI: 10.1063/1.4732070

Extended fast-ion D-alpha diagnostic on DIII-D
journal, October 2010

  • Muscatello, C. M.; Heidbrink, W. W.; Taussig, D.
  • Review of Scientific Instruments, Vol. 81, Issue 10
  • DOI: 10.1063/1.3475367

A Code that Simulates Fast-Ion D α and Neutral Particle Measurements
journal, September 2011


Measurements of the neutron source strength at DIII-D
journal, January 1997

  • Heidbrink, W. W.; Taylor, P. L.; Phillips, J. A.
  • Review of Scientific Instruments, Vol. 68, Issue 1
  • DOI: 10.1063/1.1147646

Scintillator-based diagnostic for fast ion loss measurements on DIII-D
journal, October 2010

  • Fisher, R. K.; Pace, D. C.; García-Muñoz, M.
  • Review of Scientific Instruments, Vol. 81, Issue 10
  • DOI: 10.1063/1.3490020

Radial Structure of Alfvén Eigenmodes in the DIII-D Tokamak through Electron-Cyclotron-Emission Measurements
journal, September 2006


Fast particle finite orbit width and Larmor radius effects on low- n toroidicity induced Alfvén eigenmode excitation
journal, July 1999

  • Gorelenkov, N. N.; Cheng, C. Z.; Fu, G. Y.
  • Physics of Plasmas, Vol. 6, Issue 7
  • DOI: 10.1063/1.873545

Particle distribution modification by low amplitude modes
journal, March 2010


A reduced fast ion transport model for the tokamak transport code TRANSP
journal, April 2014


Integrated modeling applications for tokamak experiments with OMFIT
journal, July 2015


Kinetic transport simulation of energetic particles
journal, April 2016


    Works referencing / citing this record:

    A measure of fast ion beta at marginal stability in the reversed field pinch
    journal, June 2019


    A measure of fast ion beta at marginal stability in the reversed field pinch
    journal, June 2019