Electromechanical modelling and design for phase control of locked modes in the DIII-D tokamak

Olofsson, K. E. J.; Choi, W.; Humphreys, D. A.; La Haye, R. J.; Shiraki, D.; Sweeney, R.; Volpe, F. A.; Welander, A. S.

doi:10.1088/0741-3335/58/4/045008

Title: Electromechanical modelling and design for phase control of locked modes in the DIII-D tokamak

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Abstract

A basic nonlinear electromechanical model is developed for the interaction between a pre-existing near-saturated tearing-mode, a conducting wall, active coils internal to the wall, and active coils external to the wall. The tearing-mode is represented by a perturbed helical surface current and its island has a small but finite moment of inertia. The model is shown to have several properties that are qualitatively consistent with the experimental observations of mode-wall and mode-coil interactions. The main purpose of the model is to guide the design of a phase control system for locked modes (LMs) in tokamaks. Such a phase controller may become an important component in integrated disruption avoidance systems. A realistic feedback controller for the LM phase is designed and tested for the electromechanical model. The results indicate that a simple fixed-gain controller can perform phase control of LMs with a range of sizes, and at arbitrary misalignment relative to a realistically dimensioned background error field. Finally, the basic model is expected to be a useful minimal dynamical system representation also for other aspects of mode-wall-coil interactions.

Authors:

Olofsson, K. E. J. ^[1]; Choi, W. ^[2]; Humphreys, D. A. ^[3]; La Haye, R. J. ^[3]; Shiraki, D. ^[4]; Sweeney, R. ^[2]; Volpe, F. A. ^[2]; Welander, A. S. ^[3]

Columbia Univ., New York, NY (United States); Oak Ridge Associated Univ., Oak Ridge, TN (United States)
Columbia Univ., New York, NY (United States)
General Atomics, San Diego, CA (United States)
Columbia Univ., New York, NY (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Publication Date:: Fri Feb 05 00:00:00 EST 2016

Research Org.:: General Atomics, San Diego, CA (United States)

Sponsoring Org.:: USDOE

Contributing Org.:: Columbia University, New York City, NY 10027, USA Present address: ORAU Oak Ridge Associated Universities, PO Box 117, Oak Ridge, TN 37831, USA Present address: ORNL Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

OSTI Identifier:: 1369233

Alternate Identifier(s):: OSTI ID: 1236995

Grant/Contract Number:: FC02-04ER54698; AC05-00OR22725; AC05-06OR23100; SC0008520

Resource Type:: Accepted Manuscript

Journal Name:: Plasma Physics and Controlled Fusion

Additional Journal Information:: Journal Volume: 58; Journal Issue: 4; Related Information: K E J Olofsson, W Choi, D Humphreys, R La Haye, D Shiraki, R Sweeney, F Volpe, A Welander, Electromechanical modelling and design for phase control of locked modes in the DIII-D tokamak, (2016) Plasma Phys. Control. Fusion 58 045008, doi: 10.1088/0741-3335/58/4/045008; Journal ID: ISSN 0741-3335

Publisher:: IOP Science

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamaks; tearing modes; automatic control

Citation Formats


                    Olofsson, K. E. J., Choi, W., Humphreys, D. A., La Haye, R. J., Shiraki, D., Sweeney, R., Volpe, F. A., and Welander, A. S. Electromechanical modelling and design for phase control of locked modes in the DIII-D tokamak.  United States: N. p., 2016. 
Web.  doi:10.1088/0741-3335/58/4/045008.

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                    Olofsson, K. E. J., Choi, W., Humphreys, D. A., La Haye, R. J., Shiraki, D., Sweeney, R., Volpe, F. A., & Welander, A. S. Electromechanical modelling and design for phase control of locked modes in the DIII-D tokamak.  United States.  https://doi.org/10.1088/0741-3335/58/4/045008

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                    Olofsson, K. E. J., Choi, W., Humphreys, D. A., La Haye, R. J., Shiraki, D., Sweeney, R., Volpe, F. A., and Welander, A. S. Fri .  
"Electromechanical modelling and design for phase control of locked modes in the DIII-D tokamak".  United States.  https://doi.org/10.1088/0741-3335/58/4/045008.  https://www.osti.gov/servlets/purl/1369233.

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@article{osti_1369233,

  title        = {Electromechanical modelling and design for phase control of locked modes in the DIII-D tokamak},

  author       = {Olofsson, K. E. J. and Choi, W. and Humphreys, D. A. and La Haye, R. J. and Shiraki, D. and Sweeney, R. and Volpe, F. A. and Welander, A. S.},

  abstractNote = {A basic nonlinear electromechanical model is developed for the interaction between a pre-existing near-saturated tearing-mode, a conducting wall, active coils internal to the wall, and active coils external to the wall. The tearing-mode is represented by a perturbed helical surface current and its island has a small but finite moment of inertia. The model is shown to have several properties that are qualitatively consistent with the experimental observations of mode-wall and mode-coil interactions. The main purpose of the model is to guide the design of a phase control system for locked modes (LMs) in tokamaks. Such a phase controller may become an important component in integrated disruption avoidance systems. A realistic feedback controller for the LM phase is designed and tested for the electromechanical model. The results indicate that a simple fixed-gain controller can perform phase control of LMs with a range of sizes, and at arbitrary misalignment relative to a realistically dimensioned background error field. Finally, the basic model is expected to be a useful minimal dynamical system representation also for other aspects of mode-wall-coil interactions.},

  doi          = {10.1088/0741-3335/58/4/045008},

  journal      = {Plasma Physics and Controlled Fusion},

  number       = 4,

  volume       = 58,

  place        = {United States},

  year         = {Fri Feb 05 00:00:00 EST 2016},

  month        = {Fri Feb 05 00:00:00 EST 2016}

}

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