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Title: $$\mathscr{H}_2$$ optimal control techniques for resistive wall mode feedback in tokamaks

Abstract

DIII-D experiments show that a new, advanced algorithm improves resistive wall mode (RWM) stability control in high performance discharges using external coils. DIII-D can excite strong, locked or nearly locked external kink modes whose rotation frequencies and growth rates are on the order of the magnetic ux di usion time of the vacuum vessel wall. The VALEN RWM model has been used to gauge the e ectiveness of RWM control algorithms in tokamaks. Simulations and experiments have shown that modern control techniques like Linear Quadratic Gaussian (LQG) control will perform better, using 77% less current, than classical techniques when using control coils external to DIII-D's vacuum vessel. Experiments were conducted to develop control of a rotating n = 1 perturbation using an LQG controller derived from VALEN and external coils. Feedback using this LQG algorithm outperformed a proportional gain only controller in these perturbation experiments over a range of frequencies. Results from high N experiments also show that advanced feedback techniques using external control coils may be as e ective as internal control coil feedback using classical control techniques.

Authors:
 [1];  [2];  [2];  [2]
  1. Univ. of California, San Diego, CA (United States); columb
  2. Columbia Univ., New York, NY (United States)
Publication Date:
Research Org.:
USDOE
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1425033
Grant/Contract Number:
FC02-04ER54698
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 58; Journal Issue: 4; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Clement, Mitchell, Hanson, Jeremy, Bialek, Jim, and Navratil, Gerald. $\mathscr{H}_2$ optimal control techniques for resistive wall mode feedback in tokamaks. United States: N. p., 2018. Web. doi:10.1088/1741-4326/aaaecd.
Clement, Mitchell, Hanson, Jeremy, Bialek, Jim, & Navratil, Gerald. $\mathscr{H}_2$ optimal control techniques for resistive wall mode feedback in tokamaks. United States. doi:10.1088/1741-4326/aaaecd.
Clement, Mitchell, Hanson, Jeremy, Bialek, Jim, and Navratil, Gerald. Wed . "$\mathscr{H}_2$ optimal control techniques for resistive wall mode feedback in tokamaks". United States. doi:10.1088/1741-4326/aaaecd.
@article{osti_1425033,
title = {$\mathscr{H}_2$ optimal control techniques for resistive wall mode feedback in tokamaks},
author = {Clement, Mitchell and Hanson, Jeremy and Bialek, Jim and Navratil, Gerald},
abstractNote = {DIII-D experiments show that a new, advanced algorithm improves resistive wall mode (RWM) stability control in high performance discharges using external coils. DIII-D can excite strong, locked or nearly locked external kink modes whose rotation frequencies and growth rates are on the order of the magnetic ux di usion time of the vacuum vessel wall. The VALEN RWM model has been used to gauge the e ectiveness of RWM control algorithms in tokamaks. Simulations and experiments have shown that modern control techniques like Linear Quadratic Gaussian (LQG) control will perform better, using 77% less current, than classical techniques when using control coils external to DIII-D's vacuum vessel. Experiments were conducted to develop control of a rotating n = 1 perturbation using an LQG controller derived from VALEN and external coils. Feedback using this LQG algorithm outperformed a proportional gain only controller in these perturbation experiments over a range of frequencies. Results from high N experiments also show that advanced feedback techniques using external control coils may be as e ective as internal control coil feedback using classical control techniques.},
doi = {10.1088/1741-4326/aaaecd},
journal = {Nuclear Fusion},
number = 4,
volume = 58,
place = {United States},
year = {Wed Feb 28 00:00:00 EST 2018},
month = {Wed Feb 28 00:00:00 EST 2018}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on February 28, 2019
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