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Title: Mode rotation control in a tokamak with a feedback-driven biased electrode

Abstract

Rotation of the plasma and MHD modes in tokamaks has been shown to stabilize resistive wall and tearing modes as well as improve confinement through suppression of edge turbulence. In this work, we control mode rotation with a biased electrode inserted into the plasma of the High Beta Tokamak-Extended Pulse’s facility in conjunction with its active GPU (Graphical Processing Unit) feedback system. We first characterize a negative linear relationship between the electrode voltage and mode rotation. Using this relationship, we design, simulate, and implement a proof-of-concept, GPU-based active-control system, which shows consistent success in controlling mode rotation in both feedforward and feedback operation. Controllability is limited by operating conditions, the electrode’s voltage range, and by the electrode’s proximity to the vessel’s walls. The final control system has a 15 μs cycle time, but the addition of various signal filters results in a full cycle latency of 200 μs.

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Columbia Univ., New York, NY (United States)
  2. Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1512695
Grant/Contract Number:  
FG02-86ER53222; SC0014664
Resource Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 90; Journal Issue: 2; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English

Citation Formats

Brooks, J. W., Stewart, I. G., Boyer, M. D., Levesque, J. P., Mauel, M. E., and Navratil, G. A. Mode rotation control in a tokamak with a feedback-driven biased electrode. United States: N. p., 2019. Web. doi:10.1063/1.5062271.
Brooks, J. W., Stewart, I. G., Boyer, M. D., Levesque, J. P., Mauel, M. E., & Navratil, G. A. Mode rotation control in a tokamak with a feedback-driven biased electrode. United States. doi:10.1063/1.5062271.
Brooks, J. W., Stewart, I. G., Boyer, M. D., Levesque, J. P., Mauel, M. E., and Navratil, G. A. Fri . "Mode rotation control in a tokamak with a feedback-driven biased electrode". United States. doi:10.1063/1.5062271.
@article{osti_1512695,
title = {Mode rotation control in a tokamak with a feedback-driven biased electrode},
author = {Brooks, J. W. and Stewart, I. G. and Boyer, M. D. and Levesque, J. P. and Mauel, M. E. and Navratil, G. A.},
abstractNote = {Rotation of the plasma and MHD modes in tokamaks has been shown to stabilize resistive wall and tearing modes as well as improve confinement through suppression of edge turbulence. In this work, we control mode rotation with a biased electrode inserted into the plasma of the High Beta Tokamak-Extended Pulse’s facility in conjunction with its active GPU (Graphical Processing Unit) feedback system. We first characterize a negative linear relationship between the electrode voltage and mode rotation. Using this relationship, we design, simulate, and implement a proof-of-concept, GPU-based active-control system, which shows consistent success in controlling mode rotation in both feedforward and feedback operation. Controllability is limited by operating conditions, the electrode’s voltage range, and by the electrode’s proximity to the vessel’s walls. The final control system has a 15 μs cycle time, but the addition of various signal filters results in a full cycle latency of 200 μs.},
doi = {10.1063/1.5062271},
journal = {Review of Scientific Instruments},
number = 2,
volume = 90,
place = {United States},
year = {2019},
month = {2}
}

Journal Article:
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This content will become publicly available on February 22, 2020
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