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Title: Magnetic shear effects on plasma transport and turbulence at high electron to ion temperature ratio in DIII-D and JT-60U plasmas

Abstract

We demonstrated negative magnetic shear in DIII-D and JT-60U in order to mitigate the confinement degradation typically observed with increasing the electron to ion temperature ratio (T-e/T-i). In recent experiments in DIII-D negative central magnetic shear (NCS) discharges, the thermal transport in the internal transport barrier formed around the radius of the minimum safety factor (q(min)) remained almost constant and modestly increased in the region outside of q(min) compared to the positive shear (PS) case, when T-e/T-i increased from about 0.8 to 1.1 through electron cyclotron heating (ECH). The benefit of NCS extending into the region outside of qmin can be explained by the lower magnetic shear in the NCS plasma over the plasma radius relative to the PS plasma. Reduced confinement degradation at high T-e/T-i with NCS plasmas was commonly observed in DIII-D and JT-60U. Furthermore, the mechanism of the different transport responses between the NCS and PS plasmas has been assessed in terms of fluctuation measurements and gyrokinetic simulations in DIII-D; NCS gave a smaller rise in the low-wavenumber broadband turbulent fluctuations with the increase in T-e/T-i compared with the PS case. This is consistent with gyrokinetic simulations, and this shows a smaller rise in the growth ratesmore » of the ion temperature gradient mode in the NCS plasmas, with increasing T-e/T-i. Gyrokinetic simulations also showed a change in the stability of the electron modes with ECH applied, consistent with higher-wavenumber fluctuation measurements, although more detailed simulations are needed to give a quantitative explanation for the experimental observations. Control of q-profile and magnetic shear will allow confinement improvement in future machines with dominant electron heating.« less

Authors:
 [1];  [2];  [3]; ORCiD logo [4];  [5];  [6];  [6];  [7];  [8];  [8];  [8];  [9];  [9];  [10];  [9];  [11];  [9]; ORCiD logo [4]
+ Show Author Affiliations
  1. National Inst. for Quantum and Radiological Science and Technology, Ibaraki (Japan)
  2. Univ. of Wisconsin, Madison, WI (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  5. National Inst. for Fusion Sciences, Toki (Japan)
  6. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  7. Graduate Univ. for Advanced Studies (SOKENDAI), Toki (Japan)
  8. Univ. of California, Los Angeles, CA (United States)
  9. General Atomics, San Diego, CA (United States)
  10. Columbia Univ., New York, NY (United States)
  11. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES); USDOE National Nuclear Security Administration (NNSA); USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1353408
Alternate Identifier(s):
OSTI ID: 1374821; OSTI ID: 1374874; OSTI ID: 1779585
Report Number(s):
LLNL-JRNL-752082
Journal ID: ISSN 0029-5515
Grant/Contract Number:  
FG02-08ER54999; FG02-94ER54084; FG02-08ER54984; AC05-00OR22725; 16K06947; FG02-04ER54761; AC52-07NA27344; FC02-04ER54698; AC02-09C11466
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 5; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; thermal transport; electron heating; magnetic shear; rotation shear; asdex upgrade; d discharges; barriers; confinement; weak

Citation Formats

Yoshida, Maiko, McKee, George R., Murakami, Masanori, Grierson, Brian A., Nakata, M., Davis, Evan M., Marinoni, Alessandro, Ono, Makoto, Rhodes, Terry L., Sung, Choongki, Schmitz, Lothar, Petty, Craig C., Ferron, John R., Turco, Francesca, Garofalo, Andrea M., Holcomb, Christopher T., Collins, Cami M., and Solomon, Wayne M. Magnetic shear effects on plasma transport and turbulence at high electron to ion temperature ratio in DIII-D and JT-60U plasmas. United States: N. p., 2017. Web. doi:10.1088/1741-4326/aa611e.
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Yoshida, Maiko, McKee, George R., Murakami, Masanori, Grierson, Brian A., Nakata, M., Davis, Evan M., Marinoni, Alessandro, Ono, Makoto, Rhodes, Terry L., Sung, Choongki, Schmitz, Lothar, Petty, Craig C., Ferron, John R., Turco, Francesca, Garofalo, Andrea M., Holcomb, Christopher T., Collins, Cami M., & Solomon, Wayne M. Magnetic shear effects on plasma transport and turbulence at high electron to ion temperature ratio in DIII-D and JT-60U plasmas. United States. https://doi.org/10.1088/1741-4326/aa611e
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Yoshida, Maiko, McKee, George R., Murakami, Masanori, Grierson, Brian A., Nakata, M., Davis, Evan M., Marinoni, Alessandro, Ono, Makoto, Rhodes, Terry L., Sung, Choongki, Schmitz, Lothar, Petty, Craig C., Ferron, John R., Turco, Francesca, Garofalo, Andrea M., Holcomb, Christopher T., Collins, Cami M., and Solomon, Wayne M. Thu . "Magnetic shear effects on plasma transport and turbulence at high electron to ion temperature ratio in DIII-D and JT-60U plasmas". United States. https://doi.org/10.1088/1741-4326/aa611e. https://www.osti.gov/servlets/purl/1353408.
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@article{osti_1353408,
title = {Magnetic shear effects on plasma transport and turbulence at high electron to ion temperature ratio in DIII-D and JT-60U plasmas},
author = {Yoshida, Maiko and McKee, George R. and Murakami, Masanori and Grierson, Brian A. and Nakata, M. and Davis, Evan M. and Marinoni, Alessandro and Ono, Makoto and Rhodes, Terry L. and Sung, Choongki and Schmitz, Lothar and Petty, Craig C. and Ferron, John R. and Turco, Francesca and Garofalo, Andrea M. and Holcomb, Christopher T. and Collins, Cami M. and Solomon, Wayne M.},
abstractNote = {We demonstrated negative magnetic shear in DIII-D and JT-60U in order to mitigate the confinement degradation typically observed with increasing the electron to ion temperature ratio (T-e/T-i). In recent experiments in DIII-D negative central magnetic shear (NCS) discharges, the thermal transport in the internal transport barrier formed around the radius of the minimum safety factor (q(min)) remained almost constant and modestly increased in the region outside of q(min) compared to the positive shear (PS) case, when T-e/T-i increased from about 0.8 to 1.1 through electron cyclotron heating (ECH). The benefit of NCS extending into the region outside of qmin can be explained by the lower magnetic shear in the NCS plasma over the plasma radius relative to the PS plasma. Reduced confinement degradation at high T-e/T-i with NCS plasmas was commonly observed in DIII-D and JT-60U. Furthermore, the mechanism of the different transport responses between the NCS and PS plasmas has been assessed in terms of fluctuation measurements and gyrokinetic simulations in DIII-D; NCS gave a smaller rise in the low-wavenumber broadband turbulent fluctuations with the increase in T-e/T-i compared with the PS case. This is consistent with gyrokinetic simulations, and this shows a smaller rise in the growth rates of the ion temperature gradient mode in the NCS plasmas, with increasing T-e/T-i. Gyrokinetic simulations also showed a change in the stability of the electron modes with ECH applied, consistent with higher-wavenumber fluctuation measurements, although more detailed simulations are needed to give a quantitative explanation for the experimental observations. Control of q-profile and magnetic shear will allow confinement improvement in future machines with dominant electron heating.},
doi = {10.1088/1741-4326/aa611e},
journal = {Nuclear Fusion},
number = 5,
volume = 57,
place = {United States},
year = {Thu Mar 30 00:00:00 EDT 2017},
month = {Thu Mar 30 00:00:00 EDT 2017}
}
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Works referenced in this record:

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

Internal Transport Barriers in JET Deuterium-Tritium Plasmas
journal, June 1998

Studies on impact of electron cyclotron wave injection on the internal transport barriers in JT-60U weak shear plasmas
journal, October 2007

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

Validation studies of gyrokinetic ITG and TEM turbulence simulations in a JT-60U tokamak using multiple flux matching
journal, July 2016

Internal Transport Barrier for Electrons in JT-60U Reversed Shear Discharges
journal, March 1997

Localized measurement of short wavelength plasma fluctuations with the DIII-D phase contrast imaging diagnostic
journal, February 2009

  • Dorris, J. R.; Rost, J. C.; Porkolab, M.
  • Review of Scientific Instruments, Vol. 80, Issue 2
  • DOI: 10.1063/1.3065094

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

Modification of the Current Profile in High-Performance Plasmas using Off-Axis Electron-Cyclotron-Current Drive in DIII-D
journal, June 2003

Role of density gradient driven trapped electron mode turbulence in the H-mode inner core with electron heating
journal, May 2016

  • Ernst, D. R.; Burrell, K. H.; Guttenfelder, W.
  • Physics of Plasmas, Vol. 23, Issue 5
  • DOI: 10.1063/1.4948723

Cross-Scale Interactions between Electron and Ion Scale Turbulence in a Tokamak Plasma
journal, June 2015

Local Gyrokinetic Vlasov Simulations with Realistic Tokamak MHD Equilibria
journal, January 2014

  • Nakata, Motoki; Matsuyama, Akinobu; Aiba, Nobuyuki
  • Plasma and Fusion Research, Vol. 9, Issue 0
  • DOI: 10.1585/pfr.9.1403029

The effect of safety factor and magnetic shear on turbulent transport in nonlinear gyrokinetic simulations
journal, February 2006

  • Kinsey, J. E.; Waltz, R. E.; Candy, J.
  • Physics of Plasmas, Vol. 13, Issue 2
  • DOI: 10.1063/1.2169804

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

Role of Pressure Gradient on Intrinsic Toroidal Rotation in Tokamak Plasmas
journal, March 2008

Chapter 1: Overview and summary
journal, December 1999

  • Editors, ITER Physics Basis; Co-Chairs, ITER Physics Expert Group Chairs an; Unit, ITER Joint Central Team and Physics
  • Nuclear Fusion, Vol. 39, Issue 12
  • DOI: 10.1088/0029-5515/39/12/301

Velocity–space structures of distribution function in toroidal ion temperature gradient turbulence
journal, December 2005

Steady state H mode and T e   T i operation with internal transport barriers in ASDEX Upgrade
journal, June 2000

Transport and performance in DIII-D discharges with weak or negative central magnetic shear
journal, May 1997

  • Greenfield, C. M.; Schissel, D. P.; Stallard, B. W.
  • Physics of Plasmas, Vol. 4, Issue 5
  • DOI: 10.1063/1.872360

Physics of non-diffusive turbulent transport of momentum and the origins of spontaneous rotation in tokamaks
journal, March 2009

A frequency tunable, eight-channel correlation ECE system for electron temperature turbulence measurements on the DIII-D tokamak
journal, August 2016

  • Sung, C.; Peebles, W. A.; Wannberg, C.
  • Review of Scientific Instruments, Vol. 87, Issue 11
  • DOI: 10.1063/1.4961296

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

Density response to central electron heating: theoretical investigations and experimental observations in ASDEX Upgrade
journal, June 2004

Enhanced Confinement and Stability in DIII-D Discharges with Reversed Magnetic Shear
journal, December 1995

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    Works referencing / citing this record:

    Internal transport barrier in tokamak and helical plasmas
    journal, January 2018

    Subdominant modes and optimization trends of DIII-D reverse magnetic shear configurations
    journal, February 2019

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