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

Title: Transport barriers in bootstrap-driven tokamaks

Abstract

Experiments have demonstrated improved energy confinement due to the spontaneous formation of an internal transport barrier in high bootstrap fraction discharges. Gyro kinetic analysis, and quasilinear predictive modeling, demonstrates that the observed transport barrier is caused by the suppression of turbulence primarily from the large Shafranov shift. It is shown, that the Shafranov shift can produce a bifurcation to improved confinement in regions of positive magnetic shear or a continuous reduction in transport for weak or negative magnetic shear. Operation at high safety factor lowers the pressure gradient threshold for the Shafranov shift driven barrier formation. Two self-organized states of the internal and edge transport barrier are observed. It is further shown that these two states are controlled by the interaction of the bootstrap current with magnetic shear, and the kinetic ballooning mode instability boundary. Election scale energy transport is shown to be dominant in inner 60% of the profile. Energetic particle driven instabilities could also be playing a role in the thermal energy transport in this region.

Authors:
ORCiD logo [1];  [1]; ORCiD logo [2];  [1];  [1]; ORCiD logo [1]
  1. General Atomics, San Diego, CA (United States)
  2. Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics (IPP)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1459670
Alternate Identifier(s):
OSTI ID: 1438969
Grant/Contract Number:  
FC02-04ER54698; FG02-95ER54309
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 25; Journal Issue: 5; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; plasma flows; energy transfer; plasma confinement; tokamaks; plasma instabilities; electric currents; self assembly; electrostatics

Citation Formats

Staebler, G. M., Garofalo, A. M., Pan, C., McClenaghan, J., Van Zeeland, M. A., and Lao, L. L. Transport barriers in bootstrap-driven tokamaks. United States: N. p., 2018. Web. doi:10.1063/1.5019282.
Staebler, G. M., Garofalo, A. M., Pan, C., McClenaghan, J., Van Zeeland, M. A., & Lao, L. L. Transport barriers in bootstrap-driven tokamaks. United States. doi:10.1063/1.5019282.
Staebler, G. M., Garofalo, A. M., Pan, C., McClenaghan, J., Van Zeeland, M. A., and Lao, L. L. Thu . "Transport barriers in bootstrap-driven tokamaks". United States. doi:10.1063/1.5019282. https://www.osti.gov/servlets/purl/1459670.
@article{osti_1459670,
title = {Transport barriers in bootstrap-driven tokamaks},
author = {Staebler, G. M. and Garofalo, A. M. and Pan, C. and McClenaghan, J. and Van Zeeland, M. A. and Lao, L. L.},
abstractNote = {Experiments have demonstrated improved energy confinement due to the spontaneous formation of an internal transport barrier in high bootstrap fraction discharges. Gyro kinetic analysis, and quasilinear predictive modeling, demonstrates that the observed transport barrier is caused by the suppression of turbulence primarily from the large Shafranov shift. It is shown, that the Shafranov shift can produce a bifurcation to improved confinement in regions of positive magnetic shear or a continuous reduction in transport for weak or negative magnetic shear. Operation at high safety factor lowers the pressure gradient threshold for the Shafranov shift driven barrier formation. Two self-organized states of the internal and edge transport barrier are observed. It is further shown that these two states are controlled by the interaction of the bootstrap current with magnetic shear, and the kinetic ballooning mode instability boundary. Election scale energy transport is shown to be dominant in inner 60% of the profile. Energetic particle driven instabilities could also be playing a role in the thermal energy transport in this region.},
doi = {10.1063/1.5019282},
journal = {Physics of Plasmas},
number = 5,
volume = 25,
place = {United States},
year = {2018},
month = {5}
}

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

Citation Metrics:
Cited by: 3 works
Citation information provided by
Web of Science

Figures / Tables:

Figure 1 Figure 1: Curve fits to measured profiles of the (a) electron temperature, (b) ion temperature, (c) electron density, (d) toroidal velocity of carbon for the strong ITB (black) and weak ITB (gray) discharges.

Save / Share:

Works referenced in this record:

Synergism between cross-section and profile shaping in beta optimization of tokamak equilibria with negative central shear
journal, October 1998


Turbulence in high-beta ASDEX upgrade advanced scenarios
journal, December 2017


An Eulerian gyrokinetic-Maxwell solver
journal, April 2003


Advances in the high bootstrap fraction regime on DIII-D towards the Q   =  5 mission of ITER steady state
journal, March 2017


Bounce averaged trapped electron fluid equations for plasma turbulence
journal, November 1996

  • Beer, M. A.; Hammett, G. W.
  • Physics of Plasmas, Vol. 3, Issue 11
  • DOI: 10.1063/1.871574

Impact of the α parameter on the microstability of internal transport barriers
journal, February 2005


Alfvén eigenmode stability and critical gradient energetic particle transport using the Trapped-Gyro-Landau-Fluid model
journal, July 2017

  • Sheng, He; Waltz, R. E.; Staebler, G. M.
  • Physics of Plasmas, Vol. 24, Issue 7
  • DOI: 10.1063/1.4989716

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

A high-accuracy Eulerian gyrokinetic solver for collisional plasmas
journal, November 2016


The quiescent double barrier regime in DIII-D
journal, April 2002

  • Greenfield, C. M.; Burrell, K. H.; Doyle, E. J.
  • Plasma Physics and Controlled Fusion, Vol. 44, Issue 5A
  • DOI: 10.1088/0741-3335/44/5A/308

A model of the saturation of coupled electron and ion scale gyrokinetic turbulence
journal, May 2017


Gyrokinetic simulation of global and local Alfvén eigenmodes driven by energetic particles in a DIII-D discharge
journal, January 2013

  • Bass, E. M.; Waltz, R. E.
  • Physics of Plasmas, Vol. 20, Issue 1
  • DOI: 10.1063/1.4773177

Development of high poloidal beta, steady-state scenario with ITER-like tungsten divertor on EAST
journal, June 2017


Shear, Periodicity, and Plasma Ballooning Modes
journal, February 1978


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

Progress toward steady-state tokamak operation exploiting the high bootstrap current fraction regime
journal, June 2016

  • Ren, Q. L.; Garofalo, A. M.; Gong, X. Z.
  • Physics of Plasmas, Vol. 23, Issue 6
  • DOI: 10.1063/1.4948724

Quiescent double barrier high-confinement mode plasmas in the DIII-D tokamak
journal, May 2001

  • Burrell, K. H.; Austin, M. E.; Brennan, D. P.
  • Physics of Plasmas, Vol. 8, Issue 5
  • DOI: 10.1063/1.1355981

Transport modeling of the DIII-D high ${{\beta}_{p}}$ scenario and extrapolations to ITER steady-state operation
journal, August 2017


Multi-scale gyrokinetic simulation of tokamak plasmas: enhanced heat loss due to cross-scale coupling of plasma turbulence
journal, December 2015


The role of zonal flows in the saturation of multi-scale gyrokinetic turbulence
journal, June 2016

  • Staebler, G. M.; Candy, J.; Howard, N. T.
  • Physics of Plasmas, Vol. 23, Issue 6
  • DOI: 10.1063/1.4954905

Electromagnetic stabilization of tokamak microturbulence in a high- β regime
journal, November 2014


Kinetic calculation of neoclassical transport including self-consistent electron and impurity dynamics
journal, July 2008


Confinement improvement in the high poloidal beta regime on DIII-D and application to steady-state H-mode on EAST
journal, May 2017

  • Ding, S.; Garofalo, A. M.; Qian, J.
  • Physics of Plasmas, Vol. 24, Issue 5
  • DOI: 10.1063/1.4982058

Compatibility of internal transport barrier with steady-state operation in the high bootstrap fraction regime on DIII-D
journal, November 2015


Noncircular, finite aspect ratio, local equilibrium model
journal, April 1998

  • Miller, R. L.; Chu, M. S.; Greene, J. M.
  • Physics of Plasmas, Vol. 5, Issue 4
  • DOI: 10.1063/1.872666

    Works referencing / citing this record:

    Progress of physics understanding for long pulse high-performance plasmas on EAST towards the steady-state operation of ITER and CFETR
    journal, December 2019

    • Huang, J.; Gong, X.; Garofalo, A. M.
    • Plasma Physics and Controlled Fusion, Vol. 62, Issue 1
    • DOI: 10.1088/1361-6587/ab56a5

    Key effects on the confinement improvement of the ASDEX Upgrade hybrid scenario
    journal, September 2019


    The dominant micro-turbulence instabilities in the lower q 95 high β p plasmas on DIII-D and predict-first extrapolation
    journal, November 2019