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Title: INCREASED STABLE BETA IN DIII-D BY SUPPRESSION OF A NEOCLASSICAL TEARING MODE USING ELECTRON CYCLOTRON CURRENT DRIVE AND ACTIVE FEEDBACK

Abstract

OAK A271 INCREASED STABLE BETA IN DIII-D BY SUPPRESSION OF A NEOCLASSICAL TEARING MODE USING ELECTRON CYCLOTRON CURRENT DRIVE AND ACTIVE FEEDBACK. In DIII-D, the first real-time active control of the electron cyclotron current drive stabilization of a neoclassical tearing mode (here m/n=3/2) is demonstrated. The plasma control system is put into a search and suppress mode to align the ECCD with the island by making either small rigid radial position shifts (of order 1 cm) of the entire plasma (and thus the island) or small changes in toroidal field (of order 0.5%) which radially moves the second harmonic resonance location (and thus the rf current drive). The optimum position minimizes the real-time mode amplitude signal and stabilization occurs despite changes in island location from discharge-to-discharge or from time-to-time. When the neutral beam heating power is programmed to rise after mode suppression by the ECCD, the plasma pressure increases above the peak at the onset of the neoclassical tearing mode until the magnetic island reappears due to the ECCD no longer being on the optimal position. Real-time tracking of the change in location of q=3/2 due to the Shafranov shift with increasing beta is necessary to position the ECCD inmore » the absence of a mode so that higher stable beta can be sustained. The control techniques developed for the m/n=3/2 NTM are also being applied to the more deleterious m/n-2/1 NTM. For the first time in any tokamak, an m/n=2/1 mode has been completely suppressed using radially localized off-axis ECCD.« less

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
GENERAL ATOMICS (US)
Sponsoring Org.:
(US)
OSTI Identifier:
813654
DOE Contract Number:  
AC03-99ER54463
Resource Type:
Conference
Resource Relation:
Conference: THIS IS A PREPRINT OF A PAPER TO BE PRESENTED AT THE 19TH IAEA FUSION ENERGY CONFERENCE, LYON (FR), 10/14/2002--10/19/2002; Other Information: PBD: 1 Sep 2002
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; AMPLITUDES; CONTROL SYSTEMS; CYCLOTRONS; DOUBLET-3 DEVICE; ELECTRONS; HARMONICS; HEATING; IAEA; MAGNETIC ISLANDS; PLASMA PRESSURE; RESONANCE; STABILIZATION; THERMONUCLEAR REACTORS

Citation Formats

LAHAYE, RJ, HUMPHREYS, DA, LOHR, J, LUCE, TC, PERKINS, FW, PETTY, CC, PRATER, R, and STRAIT, EJ. INCREASED STABLE BETA IN DIII-D BY SUPPRESSION OF A NEOCLASSICAL TEARING MODE USING ELECTRON CYCLOTRON CURRENT DRIVE AND ACTIVE FEEDBACK. United States: N. p., 2002. Web.
LAHAYE, RJ, HUMPHREYS, DA, LOHR, J, LUCE, TC, PERKINS, FW, PETTY, CC, PRATER, R, & STRAIT, EJ. INCREASED STABLE BETA IN DIII-D BY SUPPRESSION OF A NEOCLASSICAL TEARING MODE USING ELECTRON CYCLOTRON CURRENT DRIVE AND ACTIVE FEEDBACK. United States.
LAHAYE, RJ, HUMPHREYS, DA, LOHR, J, LUCE, TC, PERKINS, FW, PETTY, CC, PRATER, R, and STRAIT, EJ. Sun . "INCREASED STABLE BETA IN DIII-D BY SUPPRESSION OF A NEOCLASSICAL TEARING MODE USING ELECTRON CYCLOTRON CURRENT DRIVE AND ACTIVE FEEDBACK". United States. https://www.osti.gov/servlets/purl/813654.
@article{osti_813654,
title = {INCREASED STABLE BETA IN DIII-D BY SUPPRESSION OF A NEOCLASSICAL TEARING MODE USING ELECTRON CYCLOTRON CURRENT DRIVE AND ACTIVE FEEDBACK},
author = {LAHAYE, RJ and HUMPHREYS, DA and LOHR, J and LUCE, TC and PERKINS, FW and PETTY, CC and PRATER, R and STRAIT, EJ},
abstractNote = {OAK A271 INCREASED STABLE BETA IN DIII-D BY SUPPRESSION OF A NEOCLASSICAL TEARING MODE USING ELECTRON CYCLOTRON CURRENT DRIVE AND ACTIVE FEEDBACK. In DIII-D, the first real-time active control of the electron cyclotron current drive stabilization of a neoclassical tearing mode (here m/n=3/2) is demonstrated. The plasma control system is put into a search and suppress mode to align the ECCD with the island by making either small rigid radial position shifts (of order 1 cm) of the entire plasma (and thus the island) or small changes in toroidal field (of order 0.5%) which radially moves the second harmonic resonance location (and thus the rf current drive). The optimum position minimizes the real-time mode amplitude signal and stabilization occurs despite changes in island location from discharge-to-discharge or from time-to-time. When the neutral beam heating power is programmed to rise after mode suppression by the ECCD, the plasma pressure increases above the peak at the onset of the neoclassical tearing mode until the magnetic island reappears due to the ECCD no longer being on the optimal position. Real-time tracking of the change in location of q=3/2 due to the Shafranov shift with increasing beta is necessary to position the ECCD in the absence of a mode so that higher stable beta can be sustained. The control techniques developed for the m/n=3/2 NTM are also being applied to the more deleterious m/n-2/1 NTM. For the first time in any tokamak, an m/n=2/1 mode has been completely suppressed using radially localized off-axis ECCD.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2002},
month = {9}
}

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