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Title: Stabilization of the external kink and control of the resistive wall mode in tokamaks

Abstract

One promising approach to maintaining stability of high beta tokamak plasmas is the use of a conducting wall near the plasma to stabilize low-n ideal MHD instabilities. However, with a resistive wall, either plasma rotation or active feedback control is required to stabilize the more slowly growing resistive wall modes (RWMs). Experiments in the DIII-D, PBHX-M, and HBT-EP tokamaks have demonstrated that plasmas with a nearby conducting wall can remain stable to the n = 1 ideal external kink above the beta limit predicted with the wall at infinity, with durations in DIII-D up to 30 times {tau}{sub w}, the resistive wall time constant. More recently, detailed, reproducible observation of the n = 1 RWM has been possible in DIII-D plasmas above the no-wall beta limit. The DIII-D measurements confirm characteristics common to several RWM theories. The mode is destabilized as the plasma rotation at the q = 3 surface decreases below a critical frequency of 1 to 7 kHz. The measured mode growth times of 2 to 8 ms agree with measurements and numerical calculations of the dominant DIII-D vessel eigenmode time constants, {tau}{sub w}. From its onset, the RWM has little or no toroidal rotation and rapidly reducesmore » the plasma rotation to zero. Both DIII-D and HBT-EP have adopted the smart shell concept as an initial approach to control of these slowly growing RWMs; external coils are controlled by a feedback loop designed to make the resistive wall appear perfectly conducting by maintaining a net zero radial field at the wall. Initial experiment results from DIII-D have yielded encouraging results.« less

Authors:
 [1]; ;  [2]
  1. Columbia Univ., New York, NY (United States)
  2. General Atomics, San Diego, CA (United States); and others
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States); Columbia Univ., New York, NY (United States); Univ. of Texas, Austin, TX (United States); Princeton Univ., Princeton Plasma Physics Lab., NJ (United States); Oak Ridge National Lab., TN (United States); Lawrence Livermore National Lab., CA (United States)
Sponsoring Org.:
USDOE Office of Energy Research, Washington, DC (United States)
OSTI Identifier:
304174
Report Number(s):
GA-A23023; CONF-981127-
ON: DE99001451; TRN: 99:003147
DOE Contract Number:  
FG02-89ER53297; FG03-97ER54415; AC03-89ER51114; AC02-76CH03073; AC05-96OR22464; W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: 40. annual physics of plasmas meeting, APS Division of Plasma Physics, New Orleans, LA (United States), 16-20 Nov 1998; Other Information: PBD: Jan 1999
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; DOUBLET-3 DEVICE; PBX DEVICES; TOKAMAK DEVICES; STABILIZATION; KINK INSTABILITY; ROTATING PLASMA; INSTABILITY GROWTH RATES; FEEDBACK; CONTROL SYSTEMS; PLASMA INSTABILITY

Citation Formats

Garofalo, A M, Turnbull, A D, and Strait, E J. Stabilization of the external kink and control of the resistive wall mode in tokamaks. United States: N. p., 1999. Web.
Garofalo, A M, Turnbull, A D, & Strait, E J. Stabilization of the external kink and control of the resistive wall mode in tokamaks. United States.
Garofalo, A M, Turnbull, A D, and Strait, E J. Fri . "Stabilization of the external kink and control of the resistive wall mode in tokamaks". United States. https://www.osti.gov/servlets/purl/304174.
@article{osti_304174,
title = {Stabilization of the external kink and control of the resistive wall mode in tokamaks},
author = {Garofalo, A M and Turnbull, A D and Strait, E J},
abstractNote = {One promising approach to maintaining stability of high beta tokamak plasmas is the use of a conducting wall near the plasma to stabilize low-n ideal MHD instabilities. However, with a resistive wall, either plasma rotation or active feedback control is required to stabilize the more slowly growing resistive wall modes (RWMs). Experiments in the DIII-D, PBHX-M, and HBT-EP tokamaks have demonstrated that plasmas with a nearby conducting wall can remain stable to the n = 1 ideal external kink above the beta limit predicted with the wall at infinity, with durations in DIII-D up to 30 times {tau}{sub w}, the resistive wall time constant. More recently, detailed, reproducible observation of the n = 1 RWM has been possible in DIII-D plasmas above the no-wall beta limit. The DIII-D measurements confirm characteristics common to several RWM theories. The mode is destabilized as the plasma rotation at the q = 3 surface decreases below a critical frequency of 1 to 7 kHz. The measured mode growth times of 2 to 8 ms agree with measurements and numerical calculations of the dominant DIII-D vessel eigenmode time constants, {tau}{sub w}. From its onset, the RWM has little or no toroidal rotation and rapidly reduces the plasma rotation to zero. Both DIII-D and HBT-EP have adopted the smart shell concept as an initial approach to control of these slowly growing RWMs; external coils are controlled by a feedback loop designed to make the resistive wall appear perfectly conducting by maintaining a net zero radial field at the wall. Initial experiment results from DIII-D have yielded encouraging results.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {1}
}

Conference:
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