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

Title: L – H transition trigger physics in ITER-similar plasmas with applied n = 3 magnetic perturbations

Abstract

In this work, the L – H transition power threshold ΡLH is observed to increase with applied n = 3 Resonant Magnetic Perturbations (RMP) in ITER-similar-shape (ISS) plasmas with balanced neutral beam torque injection in DIII-D. The increase is most pronounced with added ECH: ΡLH increases with decreasing edge plasma collisionality as ΡLH/ΡLH-08 ~ (v*)-0.5, where ΡLH-08 is the 2008 ITPA multi-machine power threshold scaling. This result raises concerns for H-mode access at low edge collisionality in ITER, where resonant magnetic perturbations (RMP) may have to be applied before the L – H transition to safely suppress the first ELM. Non-axisymmetric modifications with RMP include a simultaneous reduction of the radial electric field (Er) well depth and E × B shear. This can be attributed to increasing edge toroidal co-current rotation, and is consistent with substantially increased local long-wavelength turbulence [measured via Beam Emission Spectroscopy (BES)]. At high RMP perturbation strength the edge electric field Er reverses sign locally (becomes positive), with changes in dominant turbulence modes. Edge magnetic stochasticity provides an attractive explanation of the observed modifications, and the observed changes in toroidal rotation and Er are consistent with a simple fluid model describing radial electron current flow alongmore » stochastic fieldlines. The observed collisionality dependence of the L-mode edge electric field with applied RMP is also qualitatively consistent with this model. Reflectometry data indicate a significant reduction of the normalized L-mode radial density gradient a/Ln at high RMP field with simultaneous increase in radial particle flux and electron thermal flux from power balance analysis. We conjecture that the increase of ΡLH with RMP results from the combined effects of reduced E × B flow shear (increasing turbulent transport levels) and toroidal/poloidal flow modulation due to edge stochasticity. Initial experiments indicate that non-resonant n = 3 magnetic perturbations lead only to relatively small changes in Er, E × B shear and fluctuation characteristics, and have less impact on the L – H transition power threshold. In conclusion, this motivates further exploration of the RMP spectrum dependence of ΡLH for possible mitigation of the observed threshold increase.« less

Authors:
ORCiD logo [1];  [2];  [3];  [1];  [1];  [2];  [2]; ORCiD logo [4]; ORCiD logo [4];  [4]; ORCiD logo [4]; ORCiD logo [4]; ORCiD logo [5];  [6]
  1. Univ. of California, Los Angeles, CA (United States)
  2. Univ. of Wisconsin, Madison, WI (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. General Atomics, San Diego, CA (United States)
  5. Univ. of California San Diego, La Jolla, CA (United States)
  6. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
OSTI Identifier:
1569024
Grant/Contract Number:  
FC02-04ER54698; FG02-08ER54984; FG02-89ER53296; FG02-08ER54999; AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 59; Journal Issue: 12; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; L-H transition; Resonant magnetic perturbations; Turbulence

Citation Formats

Schmitz, L., Kriete, D. M., Wilcox, R. S., Rhodes, T. L., Zeng, L., Yan, Z., McKee, G. R., Evans, T. E., Paz-Soldan, C., Gohil, P., Lyons, B., Petty, C. C., Orlov, D., and Marinoni, A. L – H transition trigger physics in ITER-similar plasmas with applied n = 3 magnetic perturbations. United States: N. p., 2019. Web. doi:10.1088/1741-4326/ab36bf.
Schmitz, L., Kriete, D. M., Wilcox, R. S., Rhodes, T. L., Zeng, L., Yan, Z., McKee, G. R., Evans, T. E., Paz-Soldan, C., Gohil, P., Lyons, B., Petty, C. C., Orlov, D., & Marinoni, A. L – H transition trigger physics in ITER-similar plasmas with applied n = 3 magnetic perturbations. United States. doi:10.1088/1741-4326/ab36bf.
Schmitz, L., Kriete, D. M., Wilcox, R. S., Rhodes, T. L., Zeng, L., Yan, Z., McKee, G. R., Evans, T. E., Paz-Soldan, C., Gohil, P., Lyons, B., Petty, C. C., Orlov, D., and Marinoni, A. Tue . "L – H transition trigger physics in ITER-similar plasmas with applied n = 3 magnetic perturbations". United States. doi:10.1088/1741-4326/ab36bf. https://www.osti.gov/servlets/purl/1569024.
@article{osti_1569024,
title = {L – H transition trigger physics in ITER-similar plasmas with applied n = 3 magnetic perturbations},
author = {Schmitz, L. and Kriete, D. M. and Wilcox, R. S. and Rhodes, T. L. and Zeng, L. and Yan, Z. and McKee, G. R. and Evans, T. E. and Paz-Soldan, C. and Gohil, P. and Lyons, B. and Petty, C. C. and Orlov, D. and Marinoni, A.},
abstractNote = {In this work, the L – H transition power threshold ΡLH is observed to increase with applied n = 3 Resonant Magnetic Perturbations (RMP) in ITER-similar-shape (ISS) plasmas with balanced neutral beam torque injection in DIII-D. The increase is most pronounced with added ECH: ΡLH increases with decreasing edge plasma collisionality as ΡLH/ΡLH-08 ~ (v*)-0.5, where ΡLH-08 is the 2008 ITPA multi-machine power threshold scaling. This result raises concerns for H-mode access at low edge collisionality in ITER, where resonant magnetic perturbations (RMP) may have to be applied before the L – H transition to safely suppress the first ELM. Non-axisymmetric modifications with RMP include a simultaneous reduction of the radial electric field (Er) well depth and E × B shear. This can be attributed to increasing edge toroidal co-current rotation, and is consistent with substantially increased local long-wavelength turbulence [measured via Beam Emission Spectroscopy (BES)]. At high RMP perturbation strength the edge electric field Er reverses sign locally (becomes positive), with changes in dominant turbulence modes. Edge magnetic stochasticity provides an attractive explanation of the observed modifications, and the observed changes in toroidal rotation and Er are consistent with a simple fluid model describing radial electron current flow along stochastic fieldlines. The observed collisionality dependence of the L-mode edge electric field with applied RMP is also qualitatively consistent with this model. Reflectometry data indicate a significant reduction of the normalized L-mode radial density gradient a/Ln at high RMP field with simultaneous increase in radial particle flux and electron thermal flux from power balance analysis. We conjecture that the increase of ΡLH with RMP results from the combined effects of reduced E × B flow shear (increasing turbulent transport levels) and toroidal/poloidal flow modulation due to edge stochasticity. Initial experiments indicate that non-resonant n = 3 magnetic perturbations lead only to relatively small changes in Er, E × B shear and fluctuation characteristics, and have less impact on the L – H transition power threshold. In conclusion, this motivates further exploration of the RMP spectrum dependence of ΡLH for possible mitigation of the observed threshold increase.},
doi = {10.1088/1741-4326/ab36bf},
journal = {Nuclear Fusion},
number = 12,
volume = 59,
place = {United States},
year = {2019},
month = {9}
}

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:

Quiescent H-mode operation using torque from non-axisymmetric, non-resonant magnetic fields
journal, June 2013


Performance and data analysis aspects of the new DIII-D monostatic profile reflectometer system
journal, November 2014

  • Zeng, L.; Peebles, W. A.; Doyle, E. J.
  • Review of Scientific Instruments, Vol. 85, Issue 11
  • DOI: 10.1063/1.4889775

Helical variation of density profiles and fluctuations in the tokamak pedestal with applied 3D fields and implications for confinement
journal, May 2018

  • Wilcox, R. S.; Rhodes, T. L.; Shafer, M. W.
  • Physics of Plasmas, Vol. 25, Issue 5
  • DOI: 10.1063/1.5024378

Neoclassical toroidal viscosity and error-field penetration in tokamaks
journal, May 2008

  • Cole, A. J.; Hegna, C. C.; Callen, J. D.
  • Physics of Plasmas, Vol. 15, Issue 5
  • DOI: 10.1063/1.2838241

Neoclassical Transport in Tokamaks in Banana/Plateau Regimes
journal, September 1972


The space potential in the tokamak text
journal, December 1991

  • Yang, X. Z.; Zhang, B. Z.; Wootton, A. J.
  • Physics of Fluids B: Plasma Physics, Vol. 3, Issue 12
  • DOI: 10.1063/1.859774

Electron Dynamics Associated with Stochastic Magnetic and Ambipolar Electric Fields
journal, July 1981


Change of the Magnetic-Field Topology by an Ergodic Divertor and the Effect on the Plasma Structure and Transport
journal, January 2006


Calculations of two-fluid linear response to non-axisymmetric fields in tokamaks
journal, May 2012


L-H transition physics in hydrogen and deuterium: key role of the edge radial electric field and ion heat flux
journal, October 2015


Modeling of stochastic magnetic flux loss from the edge of a poloidally diverted tokamak
journal, December 2002

  • Evans, T. E.; Moyer, R. A.; Monat, P.
  • Physics of Plasmas, Vol. 9, Issue 12
  • DOI: 10.1063/1.1521125

The spectral basis of optimal error field correction on DIII-D
journal, April 2014


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

Dependence of the L- to H-mode power threshold on toroidal rotation and the link to edge turbulence dynamics
journal, September 2009


Impact of magnetic perturbation coils on the edge radial electric field and turbulence in ASDEX Upgrade
journal, November 2014


Main ion and impurity edge profile evolution across the L- to H-mode transition on DIII-D
journal, August 2018

  • Haskey, S. R.; Grierson, B. A.; Chrystal, C.
  • Plasma Physics and Controlled Fusion, Vol. 60, Issue 10
  • DOI: 10.1088/1361-6587/aad702

Feedback control of the proximity to marginal RWM stability using active MHD spectroscopy
journal, November 2011


RMP ELM suppression in DIII-D plasmas with ITER similar shapes and collisionalities
journal, January 2008


Experimental evidence for the key role of the ion heat channel in the physics of the L–H transition
journal, May 2014


High-Frequency Coherent Edge Fluctuations in a High-Pedestal-Pressure Quiescent H-Mode Plasma
journal, July 2011


L–H transition studies on DIII-D to determine H-mode access for operational scenarios in ITER
journal, August 2011


Electron Heat Transport in a Tokamak with Destroyed Magnetic Surfaces
journal, January 1978


A novel, multichannel, comb-frequency Doppler backscatter system
journal, October 2010

  • Peebles, W. A.; Rhodes, T. L.; Hillesheim, J. C.
  • Review of Scientific Instruments, Vol. 81, Issue 10
  • DOI: 10.1063/1.3464266

Impact of resonant magnetic perturbations on the L-H transition on MAST
journal, June 2015


Simultaneous measurement of magnetic and density fluctuations via cross-polarization scattering and Doppler backscattering on the DIII-D tokamak
journal, September 2016

  • Rhodes, T. L.; Barada, K.; Peebles, W. A.
  • Review of Scientific Instruments, Vol. 87, Issue 11
  • DOI: 10.1063/1.4960601

Observation of Plasma Rotation Driven by Static Nonaxisymmetric Magnetic Fields in a Tokamak
journal, November 2008


Wide-field turbulence imaging with beam emission spectroscopy
journal, October 2010

  • McKee, G. R.; Fonck, R. J.; Shafer, M. W.
  • Review of Scientific Instruments, Vol. 81, Issue 10
  • DOI: 10.1063/1.3495788

Determination of the stochastic layer properties induced by magnetic perturbations via heat pulse experiments at ASDEX upgrade
journal, August 2017


Effects of applied error fields on the H-mode power threshold of JFT-2M
journal, August 1991


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


Survey of the H-mode power threshold and transition physics studies in ASDEX Upgrade
journal, September 2013


Internal Magnetic Turbulence Measurement in Plasma by Cross Polarization Scattering
journal, August 1995


Modification of the edge transport barrier by resonant magnetic perturbations
journal, February 2010


Electron thermal confinement studies with applied resonant fields on TEXT
journal, April 1989


Three-dimensional edge transport simulations for DIII-D plasmas with resonant magnetic perturbations
journal, February 2010


Flow shear induced fluctuation suppression in finite aspect ratio shaped tokamak plasma
journal, May 1995

  • Hahm, T. S.; Burrell, K. H.
  • Physics of Plasmas, Vol. 2, Issue 5
  • DOI: 10.1063/1.871313

Helical temperature perturbations associated with tearing modes in tokamak plasmas
journal, March 1995

  • Fitzpatrick, Richard
  • Physics of Plasmas, Vol. 2, Issue 3
  • DOI: 10.1063/1.871434

Multi-field/-scale interactions of turbulence with neoclassical tearing mode magnetic islands in the DIII-D tokamak
journal, May 2017

  • Bardóczi, L.; Rhodes, T. L.; Bañón Navarro, A.
  • Physics of Plasmas, Vol. 24, Issue 5
  • DOI: 10.1063/1.4977533

Resonant magnetic perturbations of edge-plasmas in toroidal confinement devices
journal, November 2015


Spatial transfer function for the beam emission spectroscopy diagnostic on DIII-D
journal, October 2006

  • Shafer, M. W.; Fonck, R. J.; McKee, G. R.
  • Review of Scientific Instruments, Vol. 77, Issue 10
  • DOI: 10.1063/1.2221908

Anomalies in the applied magnetic fields in DIII-D and their implications for the understanding of stability experiments
journal, December 2003


Impact of resonant magnetic perturbations on zonal modes, drift-wave turbulence and the L–H transition threshold
journal, November 2013


Impact of resonant magnetic perturbations on nonlinearly driven modes in drift-wave turbulence
journal, May 2012

  • Leconte, M.; Diamond, P. H.
  • Physics of Plasmas, Vol. 19, Issue 5
  • DOI: 10.1063/1.3694675

Transverse conductivity in a braided magnetic field
journal, November 1998

  • Kaganovich, I.; Rozhansky, V.
  • Physics of Plasmas, Vol. 5, Issue 11
  • DOI: 10.1063/1.873109

Overview of Experiments with the Dynamic Ergodic Divertor on TEXTOR
journal, September 2006

  • Finken, K. H.; Abdullaev, S.; Biel, W.
  • Contributions to Plasma Physics, Vol. 46, Issue 7-9
  • DOI: 10.1002/ctpp.200610038

Impact of neoclassical tearing mode–turbulence multi-scale interaction in global confinement degradation and magnetic island stability
journal, December 2017

  • Bardóczi, L.; Carter, T. A.; La Haye, R. J.
  • Physics of Plasmas, Vol. 24, Issue 12
  • DOI: 10.1063/1.5004987

Influence of the Static Dynamic Ergodic Divertor on Edge Turbulence Properties in TEXTOR
journal, October 2006


Suppression of large edge localized modes with edge resonant magnetic fields in high confinement DIII-D plasmas
journal, June 2005


L–H transition in the presence of magnetic perturbations in ASDEX Upgrade
journal, October 2012


Suppression and Mitigation of Edge Localized Modes in the DIII-D Tokamak with 3D Magnetic Perturbations
journal, January 2012


New plasma measurements with a multichannel millimeter-wave fluctuation diagnostic system in the DIII-D tokamak (invited)
journal, October 2010

  • Hillesheim, J. C.; Peebles, W. A.; Rhodes, T. L.
  • Review of Scientific Instruments, Vol. 81, Issue 10
  • DOI: 10.1063/1.3466900

Modeling of 3D magnetic equilibrium effects on edge turbulence stability during RMP ELM suppression in tokamaks
journal, July 2017


Progress in preparing scenarios for operation of the International Thermonuclear Experimental Reactor
journal, February 2015

  • Sips, A. C. C.; Giruzzi, G.; Ide, S.
  • Physics of Plasmas, Vol. 22, Issue 2
  • DOI: 10.1063/1.4904015

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

Theoretical and experimental investigations of stochastic boundaries in tokamaks
journal, October 1996


Power requirement for accessing the H-mode in ITER
journal, July 2008

  • Martin, Y. R.; Takizuka, T.; Group, the ITPA CDBM H-mode Threshold Data
  • Journal of Physics: Conference Series, Vol. 123
  • DOI: 10.1088/1742-6596/123/1/012033

Effect of resonant helical magnetic fields on plasma rotation
journal, April 2009

  • Yu, Q.; Günter, S.; Finken, K. H.
  • Physics of Plasmas, Vol. 16, Issue 4
  • DOI: 10.1063/1.3100236