Local transport barrier formation and relaxation in reverse-shear plasmas on the TFTR tokamak

Synakowski, E J; Beer, M A; Batha, S H

doi:10.2172/304147

Title: Local transport barrier formation and relaxation in reverse-shear plasmas on the TFTR tokamak

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Abstract

The roles of turbulence stabilization by sheared E x B flow and Shafranov-shift gradients are examined for TFTR. Enhanced Reverse-Shear plasmas. Both effects in combination provide the basis of a positive-feedback model that predicts reinforced turbulence suppression with increasing pressure gradient. Local fluctuation behavior at the onset of ERS confinement is consistent with this framework. The power required for transitions into the ERS regime are lower when high power neutral beams are applied earlier in the current profile evolution, consistent with the suggestion that both effects play a role. Separation of the roles of E x B and Shafranov shift effects was performed by varying the E x B shear through changes in the toroidal velocity with nearly-steady-state pressure profiles. Transport and fluctuation levels increase only when E x B shearing rates are driven below a critical value that is comparable to the fastest linear growth rates of the dominant instabilities. While a turbulence suppression criterion that involves the ratio of shearing to linear growth rates is in accord with many of these results, the existence of hidden dependencies of the criterion is suggested in experiments where the toroidal field was varied. The forward transition into the ERS regime hasmore »« less

Authors:

Synakowski, E J; Beer, M A ^[1]; Batha, S H ^[2]

Princeton Univ., NJ (United States). Princeton Plasma Physics Lab.
Fusion Physics and Technology, Torrance, CA (United States); and others

Publication Date:: 1997-02-01

Research Org.:: Princeton Univ., Princeton Plasma Physics Lab., NJ (United States)

Sponsoring Org.:: USDOE Office of Energy Research, Washington, DC (United States)

OSTI Identifier:: 304147

Report Number(s):: PPPL-3237
ON: DE97051919; TRN: 99:002002

DOE Contract Number:: AC02-76CH03073

Resource Type:: Technical Report

Resource Relation:: Other Information: PBD: Feb 1997

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION; CONFINEMENT; PLASMA DRIFT; SHEAR; TFTR TOKAMAK; PRESSURE GRADIENTS; ROTATING PLASMA; ENERGY TRANSFER; CHARGED-PARTICLE TRANSPORT; SCALING LAWS

Citation Formats


                    Synakowski, E J, Beer, M A, and Batha, S H. Local transport barrier formation and relaxation in reverse-shear plasmas on the TFTR tokamak.  United States: N. p., 1997. 
        Web.  doi:10.2172/304147.

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                    Synakowski, E J, Beer, M A, & Batha, S H. Local transport barrier formation and relaxation in reverse-shear plasmas on the TFTR tokamak.  United States.  https://doi.org/10.2172/304147

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                    Synakowski, E J, Beer, M A, and Batha, S H. 1997.  
        "Local transport barrier formation and relaxation in reverse-shear plasmas on the TFTR tokamak".  United States.  https://doi.org/10.2172/304147.  https://www.osti.gov/servlets/purl/304147.

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@article{osti_304147,

  title        = {Local transport barrier formation and relaxation in reverse-shear plasmas on the TFTR tokamak},

  author       = {Synakowski, E J and Beer, M A and Batha, S H},

  abstractNote = {The roles of turbulence stabilization by sheared E x B flow and Shafranov-shift gradients are examined for TFTR. Enhanced Reverse-Shear plasmas. Both effects in combination provide the basis of a positive-feedback model that predicts reinforced turbulence suppression with increasing pressure gradient. Local fluctuation behavior at the onset of ERS confinement is consistent with this framework. The power required for transitions into the ERS regime are lower when high power neutral beams are applied earlier in the current profile evolution, consistent with the suggestion that both effects play a role. Separation of the roles of E x B and Shafranov shift effects was performed by varying the E x B shear through changes in the toroidal velocity with nearly-steady-state pressure profiles. Transport and fluctuation levels increase only when E x B shearing rates are driven below a critical value that is comparable to the fastest linear growth rates of the dominant instabilities. While a turbulence suppression criterion that involves the ratio of shearing to linear growth rates is in accord with many of these results, the existence of hidden dependencies of the criterion is suggested in experiments where the toroidal field was varied. The forward transition into the ERS regime has also been examined in strongly rotating plasmas. The power threshold is higher with unidirectional injection than with balanced injection.},

  doi          = {10.2172/304147},

  url          = {https://www.osti.gov/biblio/304147},
  journal      = {},
number       = ,

  volume       = ,

  place        = {United States},

  year         = {1997},

  month        = {2}

}

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https://doi.org/10.2172/304147

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