Error field optimization in DIII-D using extremum seeking control

Lanctot, M. J.; Olofsson, K. E. J.; Capella, M.; Humphreys, D. A.; Eidietis, N.; Hanson, J. M.; Paz-Soldan, C.; Strait, E. J.; Walker, M. L.

doi:10.1088/0029-5515/56/7/076003

Title: Error field optimization in DIII-D using extremum seeking control

Journal Article · Fri Jun 03 00:00:00 EDT 2016 · Nuclear Fusion

DOI:https://doi.org/10.1088/0029-5515/56/7/076003· OSTI ID:1371745

Lanctot, M. J. ^[1]; Olofsson, K. E. J. ^[2]; Capella, M. ^[3]; Humphreys, D. A. ^[1]; Eidietis, N. ^[1]; Hanson, J. M. ^[4]; Paz-Soldan, C. ^[1]; Strait, E. J. ^[1]; Walker, M. L. ^[1]

General Atomics, San Diego, CA (United States)
Oak Ridge Associated Univ., Oak Ridge, TN (United States)
Univ. of California San Diego, La Jolla, CA (United States)
Columbia Univ., New York, NY (United States)

A closed-loop error field control algorithm is implemented in the Plasma Control System of the DIII-D tokamak and used to identify optimal control currents during a single plasma discharge. The algorithm, based on established extremum seeking control theory, exploits the link in tokamaks between maximizing the toroidal angular momentum and minimizing deleterious non-axisymmetric magnetic fields. Slowly-rotating n = 1 fields (the dither), generated by external coils, are used to perturb the angular momentum, monitored in real-time using a charge-exchange spectroscopy diagnostic. Simple signal processing of the rotation measurements extracts information about the rotation gradient with respect to the control coil currents. This information is used to converge the control coil currents to a point that maximizes the toroidal angular momentum. The technique is well-suited for multi-coil, multi-harmonic error field optimizations in disruption sensitive devices as it does not require triggering locked tearing modes or plasma current disruptions. Control simulations highlight the importance of the initial search direction on the rate of the convergence, and identify future algorithm upgrades that may allow more rapid convergence that projects to convergence times in ITER on the order of tens of seconds.

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

Sponsoring Organization:: USDOE

Grant/Contract Number:: FC02-04ER54698; AC05-06OR23100; FG02-04ER54761

OSTI ID:: 1371745

Alternate ID(s):: OSTI ID: 1255456

Journal Information:: Nuclear Fusion, Vol. 56, Issue 7; Related Information: M.J. Lanctot, K.E.J. Olofsson, M. Capella, D.A. Humphreys, N. Eidietis, J.M. Hanson, C. Paz-Soldan, E.J. Strait and M.L. Walker, "Error field optimization in DIII-D using extremum seeking control," Nucl. Fusion 56, 076003 (2016).; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 11 works

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