E×B Flux Driven Detachment Bifurcation in the DIII-D Tokamak

doi:10.1103/PhysRevLett.121.075001

Title: $E \times B$ Flux Driven Detachment Bifurcation in the DIII-D Tokamak

Abstract

A bifurcative step transition from low-density, high-temperature, attached divertor conditions to high-density, low-temperature, detached divertor conditions is experimentally observed in DIII-D tokamak plasmas as density is increased. The step transition is only observed in the high confinement mode and only when the B × ∇B drift is directed towards the divertor. Here, this work reports for the first time a theoretical explanation and numerical simulations that qualitatively reproduce this bifurcation and its dependence on the toroidal field direction. According to the model, the bifurcation is primarily driven by the interdependence of the E × B -drift fluxes, divertor electric potential structure, and divertor conditions. In the attached conditions, strong potential gradients in the low field side (LFS) divertor drive E × B -drift flux towards the high field side divertor, reinforcing low density, high temperature conditions in the LFS divertor leg. At the onset of detachment, reduction in the potential gradients in the LFS divertor leg reduce the E × B -drift flux as well, such that the divertor plasma evolves nonlinearly to high density, strongly detached conditions. Experimental estimates of the E × B -drift fluxes, based on divertor Thomson scattering measurements, and their dependence on the divertor conditionsmore »« less

Authors:

Jaervinen, A. E. ^[1]; Allen, S. L. ^[1]; Eldon, D. ^[1]; Fenstermacher, M. E. ^[1]; Groth, M. ^[1]; Hill, D. N. ^[1]; Leonard, A. W. ^[1]; McLean, A. G. ^[1]; Porter, G. D. ^[1]; Rognlien, T. D. ^[1]; Samuell, C. M. ^[1]; Wang, H. Q. ^[1]

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:: 2018-08-01

Research Org.:: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:: USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:: 1512600

Alternate Identifier(s):: OSTI ID: 1464582

Report Number(s):: LLNL-JRNL-741509
Journal ID: ISSN 0031-9007; PRLTAO; 891209

Grant/Contract Number:: AC52-07NA27344; FC02-04ER54698; 17-ERD-020

Resource Type:: Accepted Manuscript

Journal Name:: Physical Review Letters

Additional Journal Information:: Journal Volume: 121; Journal Issue: 7; Journal ID: ISSN 0031-9007

Publisher:: American Physical Society (APS)

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats


                    Jaervinen, A. E., Allen, S. L., Eldon, D., Fenstermacher, M. E., Groth, M., Hill, D. N., Leonard, A. W., McLean, A. G., Porter, G. D., Rognlien, T. D., Samuell, C. M., and Wang, H. Q. E×B Flux Driven Detachment Bifurcation in the DIII-D Tokamak.  United States: N. p., 2018. 
        Web.  doi:10.1103/PhysRevLett.121.075001.

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                    Jaervinen, A. E., Allen, S. L., Eldon, D., Fenstermacher, M. E., Groth, M., Hill, D. N., Leonard, A. W., McLean, A. G., Porter, G. D., Rognlien, T. D., Samuell, C. M., & Wang, H. Q. E×B Flux Driven Detachment Bifurcation in the DIII-D Tokamak.  United States.  doi:https://doi.org/10.1103/PhysRevLett.121.075001

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                    Jaervinen, A. E., Allen, S. L., Eldon, D., Fenstermacher, M. E., Groth, M., Hill, D. N., Leonard, A. W., McLean, A. G., Porter, G. D., Rognlien, T. D., Samuell, C. M., and Wang, H. Q. Wed .  
        "E×B Flux Driven Detachment Bifurcation in the DIII-D Tokamak".  United States.  doi:https://doi.org/10.1103/PhysRevLett.121.075001.  https://www.osti.gov/servlets/purl/1512600.

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@article{osti_1512600,

  title        = {E×B Flux Driven Detachment Bifurcation in the DIII-D Tokamak},

  author       = {Jaervinen, A. E. and Allen, S. L. and Eldon, D. and Fenstermacher, M. E. and Groth, M. and Hill, D. N. and Leonard, A. W. and McLean, A. G. and Porter, G. D. and Rognlien, T. D. and Samuell, C. M. and Wang, H. Q.},

  abstractNote = {A bifurcative step transition from low-density, high-temperature, attached divertor conditions to high-density, low-temperature, detached divertor conditions is experimentally observed in DIII-D tokamak plasmas as density is increased. The step transition is only observed in the high confinement mode and only when the B × ∇B drift is directed towards the divertor. Here, this work reports for the first time a theoretical explanation and numerical simulations that qualitatively reproduce this bifurcation and its dependence on the toroidal field direction. According to the model, the bifurcation is primarily driven by the interdependence of the E × B -drift fluxes, divertor electric potential structure, and divertor conditions. In the attached conditions, strong potential gradients in the low field side (LFS) divertor drive E × B -drift flux towards the high field side divertor, reinforcing low density, high temperature conditions in the LFS divertor leg. At the onset of detachment, reduction in the potential gradients in the LFS divertor leg reduce the E × B -drift flux as well, such that the divertor plasma evolves nonlinearly to high density, strongly detached conditions. Experimental estimates of the E × B -drift fluxes, based on divertor Thomson scattering measurements, and their dependence on the divertor conditions are qualitatively consistent with the numerical predictions. Finally, the implications for divertor power exhaust and detachment control in the next step fusion devices are discussed.},

  doi          = {10.1103/PhysRevLett.121.075001},

  journal      = {Physical Review Letters},

  number       = 7,

  volume       = 121,

  place        = {United States},

  year         = {2018},

  month        = {8}

}

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DOI: https://doi.org/10.1103/PhysRevLett.121.075001

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Works referencing / citing this record:

First experimental tests of a new small angle slot divertor on DIII-D
journal, July 2019

Guo, H. Y.; Wang, H. Q.; Watkins, J. G.
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First experimental tests of a new small angle slot divertor on DIII-D
journal, July 2019

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Divertor detachment and asymmetry in H-mode operation with an ITER-like tungsten divertor in EAST
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Title: E × B Flux Driven Detachment Bifurcation in the DIII-D Tokamak

Abstract

Citation Formats

A quarter-century of H-mode studies journal, November 2007

Thermal front analysis of detached divertors and MARFEs journal, October 1994

Progress at JET in integrating ITER-relevant core and edge plasmas within the constraints of an ITER-like wall journal, February 2015

Initial operation of the divertor Thomson scattering diagnostic on DIII-D journal, February 1997

Sensitivity of detachment extent to magnetic configuration and external parameters journal, April 2016

Experimentally-based ExB drifts in the DIII-D divertor and SOL calculated from integration of Ohm's law using Thomson scattering measurements of Te and ne journal, August 2017

Electron pressure balance in the SOL through the transition to detachment journal, August 2015

Model of L to H -Mode Transition in Tokamak journal, May 1988

Calculations of energy losses due to atomic processes in tokamaks with applications to the International Thermonuclear Experimental Reactor divertor journal, June 1995

Impurity release from low-Z materials under light particle bombardment journal, February 1997

Physical sputtering and reflection processes in plasma-wall interactions journal, September 1997

Pfirsch-Schluter currents in the JET divertor journal, January 1997

Partial detachment of high power discharges in ASDEX Upgrade journal, April 2015

Self-Sustained Divertor Plasma Oscillations in the JET Tokamak journal, November 1999

Controlling marginally detached divertor plasmas journal, May 2017

Two-dimensional electric fields and drifts near the magnetic separatrix in divertor tokamaks journal, May 1999

Divertor Physics Research on Alcator C-Mod journal, April 2007

Role of divertor geometry on detachment and core plasma performance in JT60U journal, March 1999

Impurity seeding for tokamak power exhaust: from present devices via ITER to DEMO journal, November 2013

Electric field-induced plasma convection in tokamak divertors journal, April 2000

Chapter 4: Power and particle control journal, June 2007

First experimental tests of a new small angle slot divertor on DIII-D journal, July 2019

First experimental tests of a new small angle slot divertor on DIII-D journal, July 2019

Neutral density estimation in the ASDEX upgrade divertor from deuterium emissivity measurements during detachment and shoulder formation journal, September 2019

DIII-D research towards establishing the scientific basis for future fusion reactors journal, June 2019

Summary of the 27th IAEA Fusion Energy Conference in the categories of EX/W, EX/D, and ICC journal, September 2019

Divertor detachment and asymmetry in H-mode operation with an ITER-like tungsten divertor in EAST journal, October 2019

Thermionic Cooling of the Target Plasma to a Sub-eV Temperature journal, January 2019

Title: $E \times B$ Flux Driven Detachment Bifurcation in the DIII-D Tokamak

A quarter-century of H-mode studies
journal, November 2007

Thermal front analysis of detached divertors and MARFEs
journal, October 1994

Progress at JET in integrating ITER-relevant core and edge plasmas within the constraints of an ITER-like wall
journal, February 2015

Initial operation of the divertor Thomson scattering diagnostic on DIII-D
journal, February 1997

Sensitivity of detachment extent to magnetic configuration and external parameters
journal, April 2016

Experimentally-based ExB drifts in the DIII-D divertor and SOL calculated from integration of Ohm's law using Thomson scattering measurements of Te and ne
journal, August 2017

Electron pressure balance in the SOL through the transition to detachment
journal, August 2015

Model of $L$ to $H$ -Mode Transition in Tokamak
journal, May 1988

Calculations of energy losses due to atomic processes in tokamaks with applications to the International Thermonuclear Experimental Reactor divertor
journal, June 1995

Impurity release from low-Z materials under light particle bombardment
journal, February 1997

Physical sputtering and reflection processes in plasma-wall interactions
journal, September 1997

Pfirsch-Schluter currents in the JET divertor
journal, January 1997

Partial detachment of high power discharges in ASDEX Upgrade
journal, April 2015

Self-Sustained Divertor Plasma Oscillations in the JET Tokamak
journal, November 1999

Controlling marginally detached divertor plasmas
journal, May 2017

Two-dimensional electric fields and drifts near the magnetic separatrix in divertor tokamaks
journal, May 1999

Divertor Physics Research on Alcator C-Mod
journal, April 2007

Role of divertor geometry on detachment and core plasma performance in JT60U
journal, March 1999

Impurity seeding for tokamak power exhaust: from present devices via ITER to DEMO
journal, November 2013

Electric field-induced plasma convection in tokamak divertors
journal, April 2000

Chapter 4: Power and particle control
journal, June 2007

First experimental tests of a new small angle slot divertor on DIII-D
journal, July 2019

First experimental tests of a new small angle slot divertor on DIII-D
journal, July 2019

Neutral density estimation in the ASDEX upgrade divertor from deuterium emissivity measurements during detachment and shoulder formation
journal, September 2019

DIII-D research towards establishing the scientific basis for future fusion reactors
journal, June 2019

Summary of the 27th IAEA Fusion Energy Conference in the categories of EX/W, EX/D, and ICC
journal, September 2019

Divertor detachment and asymmetry in H-mode operation with an ITER-like tungsten divertor in EAST
journal, October 2019

Thermionic Cooling of the Target Plasma to a Sub-eV Temperature
journal, January 2019