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

Title: Reduced electron thermal transport in low collisionality H-mode plasmas in DIII-D and the importance of TEM/ETG-scale turbulence

Abstract

The first systematic investigation of core electron thermal transport and the role of local ion temperature gradient/trapped electron mode/electron temperature gradient (ITG/TEM/ETG)-scale core turbulence is performed in high temperature, low collisionality H-mode plasmas in the DIII-D tokamak. Wavenumber spectra of L-mode and H-mode density turbulence are measured by Doppler backscattering. H-mode wavenumber spectra are directly contrasted for the first time with nonlinear gyrokinetic simulation results. Core ITG/TEM-scale turbulence is substantially reduced/suppressed by E × B shear promptly after the L–H transition, resulting in reduced electron thermal transport across the entire minor radius. For small kθρs, both experiment and nonlinear gyrokinetic simulations using the GYRO code show density fluctuation levels increasing with kθρs in H-mode (r/a = 0.6), in contrast to ITG/TEM-dominated L-mode plasmas. GYRO simulations also indicate that a significant portion of the remaining H-mode electron heat flux results directly from residual intermediate/short-scale TEM/ETG turbulence. Electron transport at substantially increased electron-to-ion temperature ratio (Te/Ti ≥ 1, r/a ≤ 0.35) has been investigated in ECH-assisted, quiescent H-mode plasmas. A synergistic increase in core electron and ion thermal diffusivity (normalized to the gyro-Bohm diffusivity) is found with applied ECH. From linear stability analysis, the TEM mode is expected to become the dominantmore » linear instability with ECH due to increased electron-to-ion temperature ratio and a reduction in the ion temperature gradient. This is consistent with increased electron temperature fluctuations and core electron thermal diffusivity observed experimentally. The reduced ion temperature gradient likely results from a reduction in the ITG critical gradient due to increased Te/Ti and reduced E × B shear. These studies are performed at collisonality ( \nu_{\rm e}^\ast \sim 0.05 , r/a ≤ 0.6) and address transport in electron heat-dominated regimes, thought to be important in ITER due to α-particle heating.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF); UT-Battelle LLC/ORNL, Oak Ridge, TN (Unted States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); General Atomics, San Diego, CA (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Univ. of California, San Diego, CA (United States); Univ. of California, Los Angeles, CA (United States); Univ. of Wisconsin, Madison, WI (United States); Univ. of Texas, Austin, TX (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1564873
DOE Contract Number:  
AC05-00OR22725; AC52-07NA27344; FC02-04ER54698; FC02-93ER54186; FG02-07ER54917; FG02-08ER54984; FG02-08ER54999; FG02-89ER53296; FG03-97ER54415
Resource Type:
Journal Article
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 52; Journal Issue: 2; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
Physics

Citation Formats

Schmitz, L., Holland, C., Rhodes, T. L., Wang, G., Zeng, L., White, A. E., Hillesheim, J. C., Peebles, W. A., Smith, S. P., Prater, R., McKee, G. R., Yan, Z., Solomon, W. M., Burrell, K. H., Holcomb, C. T., Doyle, E. J., DeBoo, J. C., Austin, M. E., deGrassie, J. S., and Petty, C. C. Reduced electron thermal transport in low collisionality H-mode plasmas in DIII-D and the importance of TEM/ETG-scale turbulence. United States: N. p., 2012. Web. doi:10.1088/0029-5515/52/2/023003.
Schmitz, L., Holland, C., Rhodes, T. L., Wang, G., Zeng, L., White, A. E., Hillesheim, J. C., Peebles, W. A., Smith, S. P., Prater, R., McKee, G. R., Yan, Z., Solomon, W. M., Burrell, K. H., Holcomb, C. T., Doyle, E. J., DeBoo, J. C., Austin, M. E., deGrassie, J. S., & Petty, C. C. Reduced electron thermal transport in low collisionality H-mode plasmas in DIII-D and the importance of TEM/ETG-scale turbulence. United States. doi:10.1088/0029-5515/52/2/023003.
Schmitz, L., Holland, C., Rhodes, T. L., Wang, G., Zeng, L., White, A. E., Hillesheim, J. C., Peebles, W. A., Smith, S. P., Prater, R., McKee, G. R., Yan, Z., Solomon, W. M., Burrell, K. H., Holcomb, C. T., Doyle, E. J., DeBoo, J. C., Austin, M. E., deGrassie, J. S., and Petty, C. C. Thu . "Reduced electron thermal transport in low collisionality H-mode plasmas in DIII-D and the importance of TEM/ETG-scale turbulence". United States. doi:10.1088/0029-5515/52/2/023003.
@article{osti_1564873,
title = {Reduced electron thermal transport in low collisionality H-mode plasmas in DIII-D and the importance of TEM/ETG-scale turbulence},
author = {Schmitz, L. and Holland, C. and Rhodes, T. L. and Wang, G. and Zeng, L. and White, A. E. and Hillesheim, J. C. and Peebles, W. A. and Smith, S. P. and Prater, R. and McKee, G. R. and Yan, Z. and Solomon, W. M. and Burrell, K. H. and Holcomb, C. T. and Doyle, E. J. and DeBoo, J. C. and Austin, M. E. and deGrassie, J. S. and Petty, C. C.},
abstractNote = {The first systematic investigation of core electron thermal transport and the role of local ion temperature gradient/trapped electron mode/electron temperature gradient (ITG/TEM/ETG)-scale core turbulence is performed in high temperature, low collisionality H-mode plasmas in the DIII-D tokamak. Wavenumber spectra of L-mode and H-mode density turbulence are measured by Doppler backscattering. H-mode wavenumber spectra are directly contrasted for the first time with nonlinear gyrokinetic simulation results. Core ITG/TEM-scale turbulence is substantially reduced/suppressed by E × B shear promptly after the L–H transition, resulting in reduced electron thermal transport across the entire minor radius. For small kθρs, both experiment and nonlinear gyrokinetic simulations using the GYRO code show density fluctuation levels increasing with kθρs in H-mode (r/a = 0.6), in contrast to ITG/TEM-dominated L-mode plasmas. GYRO simulations also indicate that a significant portion of the remaining H-mode electron heat flux results directly from residual intermediate/short-scale TEM/ETG turbulence. Electron transport at substantially increased electron-to-ion temperature ratio (Te/Ti ≥ 1, r/a ≤ 0.35) has been investigated in ECH-assisted, quiescent H-mode plasmas. A synergistic increase in core electron and ion thermal diffusivity (normalized to the gyro-Bohm diffusivity) is found with applied ECH. From linear stability analysis, the TEM mode is expected to become the dominant linear instability with ECH due to increased electron-to-ion temperature ratio and a reduction in the ion temperature gradient. This is consistent with increased electron temperature fluctuations and core electron thermal diffusivity observed experimentally. The reduced ion temperature gradient likely results from a reduction in the ITG critical gradient due to increased Te/Ti and reduced E × B shear. These studies are performed at collisonality ( \nu_{\rm e}^\ast \sim 0.05 , r/a ≤ 0.6) and address transport in electron heat-dominated regimes, thought to be important in ITER due to α-particle heating.},
doi = {10.1088/0029-5515/52/2/023003},
journal = {Nuclear Fusion},
issn = {0029-5515},
number = 2,
volume = 52,
place = {United States},
year = {2012},
month = {1}
}

Works referenced in this record:

Prediction of Significant Tokamak Turbulence at Electron Gyroradius Scales
journal, November 2002


The effect of ion-scale dynamics on electron-temperature-gradient turbulence
journal, July 2007


Coupled ion temperature gradient and trapped electron mode to electron temperature gradient mode gyrokinetic simulations
journal, May 2007

  • Waltz, R. E.; Candy, J.; Fahey, M.
  • Physics of Plasmas, Vol. 14, Issue 5
  • DOI: 10.1063/1.2436851

Scale Separation between Electron and Ion Thermal Transport
journal, May 2008


Multiscale features of density and frequency spectra from nonlinear gyrokinetics
journal, October 2008

  • Görler, T.; Jenko, F.
  • Physics of Plasmas, Vol. 15, Issue 10
  • DOI: 10.1063/1.3006086

Resolving electron scale turbulence in spherical tokamaks with flow shear
journal, February 2011

  • Guttenfelder, W.; Candy, J.
  • Physics of Plasmas, Vol. 18, Issue 2
  • DOI: 10.1063/1.3551701

Doppler reflectometry for the investigation of propagating density perturbations
journal, October 2001


A multichannel, frequency-modulated, tunable Doppler backscattering and reflectometry system
journal, August 2009

  • Hillesheim, J. C.; Peebles, W. A.; Rhodes, T. L.
  • Review of Scientific Instruments, Vol. 80, Issue 8
  • DOI: 10.1063/1.3205449

Dependence of Heat and Particle Transport on the Ratio of the Ion and Electron Temperatures
journal, November 1999


Improved Confinement with Reversed Magnetic Shear in TFTR
journal, December 1995


JETTO simulations of T e / T i effects on plasma confinement
journal, February 2005


Gyro-Landau fluid equations for trapped and passing particles
journal, October 2005

  • Staebler, G. M.; Kinsey, J. E.; Waltz, R. E.
  • Physics of Plasmas, Vol. 12, Issue 10
  • DOI: 10.1063/1.2044587

A theory-based transport model with comprehensive physics
journal, May 2007

  • Staebler, G. M.; Kinsey, J. E.; Waltz, R. E.
  • Physics of Plasmas, Vol. 14, Issue 5
  • DOI: 10.1063/1.2436852

A correlation electron cyclotron emission diagnostic and the importance of multifield fluctuation measurements for testing nonlinear gyrokinetic turbulence simulations
journal, October 2008

  • White, A. E.; Schmitz, L.; Peebles, W. A.
  • Review of Scientific Instruments, Vol. 79, Issue 10
  • DOI: 10.1063/1.2981186

Observation of Reduced Electron-Temperature Fluctuations in the Coreof H-Mode Plasmas
journal, January 2008


Ion temperature gradient turbulence simulations and plasma flux surface shape
journal, November 1999

  • Waltz, R. E.; Miller, R. L.
  • Physics of Plasmas, Vol. 6, Issue 11
  • DOI: 10.1063/1.873694

An Eulerian gyrokinetic-Maxwell solver
journal, April 2003


The first transport code simulations using the trapped gyro-Landau-fluid model
journal, May 2008

  • Kinsey, J. E.; Staebler, G. M.; Waltz, R. E.
  • Physics of Plasmas, Vol. 15, Issue 5
  • DOI: 10.1063/1.2889008

Quiescent Double Barrier Regime in the DIII-D Tokamak
journal, May 2001


The quiescent double barrier regime in the DIII-D tokamak
journal, November 2001


Edge turbulence reduction at the L-H transition in DIII-D
journal, April 1993


Scaling laws of density fluctuations at high- k on Tore Supra
journal, November 2004


Fluctuation spectra and velocity profile from Doppler backscattering on Tore Supra
journal, August 2006


Probing plasma turbulence by modulating the electron temperature gradient
journal, May 2010

  • DeBoo, J. C.; Holland, C.; Rhodes, T. L.
  • Physics of Plasmas, Vol. 17, Issue 5
  • DOI: 10.1063/1.3316298

Quiescent H-mode plasmas in the DIII-D tokamak
journal, April 2002

  • Burrell, K. H.; Austin, M. E.; Brennan, D. P.
  • Plasma Physics and Controlled Fusion, Vol. 44, Issue 5A
  • DOI: 10.1088/0741-3335/44/5A/325

Role of T e / T i and ∇ v tor in ion heat transport of ASDEX Upgrade H-mode plasmas
journal, November 2006


Linear gyrokinetic stability calculations of electron heat dominated plasmas in ASDEX Upgrade
journal, February 2005

  • Peeters, A. G.; Angioni, C.; Apostoliceanu, M.
  • Physics of Plasmas, Vol. 12, Issue 2
  • DOI: 10.1063/1.1848111

Comparison of initial value and eigenvalue codes for kinetic toroidal plasma instabilities
journal, August 1995


Diffusive particle and heat pinch effects in toroidal plasmas
journal, October 1989


Temperature ratio dependence of ion temperature gradient and trapped electron mode instability thresholds
journal, January 2008

  • Casati, Alessandro; Bourdelle, C.; Garbet, X.
  • Physics of Plasmas, Vol. 15, Issue 4
  • DOI: 10.1063/1.2906223

Fluctuation characteristics and transport properties of collisionless trapped electron mode turbulence
journal, February 2010

  • Xiao, Yong; Holod, Ihor; Zhang, Wenlu
  • Physics of Plasmas, Vol. 17, Issue 2
  • DOI: 10.1063/1.3302504

Measurements of ion temperature fluctuations in the Tokamak Fusion Test Reactor
journal, February 1998


Gyrokinetic simulation of collisionless trapped-electron mode turbulence
journal, July 2005

  • Dannert, Tilman; Jenko, Frank
  • Physics of Plasmas, Vol. 12, Issue 7
  • DOI: 10.1063/1.1947447

Simultaneous measurement of core electron temperature and density fluctuations during electron cyclotron heating on DIII-D
journal, February 2010

  • White, A. E.; Schmitz, L.; Peebles, W. A.
  • Physics of Plasmas, Vol. 17, Issue 2
  • DOI: 10.1063/1.3318469

Critical gradient formula for toroidal electron temperature gradient modes
journal, September 2001

  • Jenko, F.; Dorland, W.; Hammett, G. W.
  • Physics of Plasmas, Vol. 8, Issue 9
  • DOI: 10.1063/1.1391261

Anomalous Transport Scaling in the DIII-D Tokamak Matched by Supercomputer Simulation
journal, July 2003


Advances in validating gyrokinetic turbulence models against L- and H-mode plasmas
journal, May 2011

  • Holland, C.; Schmitz, L.; Rhodes, T. L.
  • Physics of Plasmas, Vol. 18, Issue 5
  • DOI: 10.1063/1.3574518

Nonlinear electromagnetic gyrokinetic equation for plasmas with large mean flows
journal, July 1998

  • Sugama, H.; Horton, W.
  • Physics of Plasmas, Vol. 5, Issue 7
  • DOI: 10.1063/1.872941

Gyrokinetic turbulence simulation of profile shear stabilization and broken gyroBohm scaling
journal, May 2002

  • Waltz, R. E.; Candy, J. M.; Rosenbluth, M. N.
  • Physics of Plasmas, Vol. 9, Issue 5
  • DOI: 10.1063/1.1448830

A unified method for operator evaluation in local Grad–Shafranov plasma equilibria
journal, September 2009