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Title: Resistive instabilities in negative central shear tokamaks with peaked pressure profiles

Abstract

The resistive (n = 1) instabilities in negative central shear (NCS) advanced tokamaks with peaked pressure profiles axe investigated systematically by using the MARS resistive MHD code. Two characteristically different types of resistive modes are found. One localized to the inner of the two mode rational surfaces and the other more global. The localized mode is destabilized by shear reversal and plasma pressure peaking. The mode structure has an interchange parity and corresponds to the predicted localized resistive interchange mode when the resistive interchange stability criterion is violated locally (D{sub R} > 0). In a rotating plasma, this mode rotates with the inner rational surface. The global mode has structure corresponding to the coupling of a double pitched mode with an external kink. This mode usually rotates with the outer portion of the plasma. It is destabilized by plasma beta and stabilized by wall and rotation shear. Experimentally, MHD bursts localized on the inside rational q surfaces in NCS discharges were detected prior to disruption in DIII-D. The {beta}{sub N} value at disruption has been found to be independent of q{sub min} and also decreases with p(0)/(p) in quantitative agreement with the predictions of resistive MHD theory; this constitutes themore » first positive identification of the resistive interchange mode in the tokamak plasma. The resistive {beta} limit is typically 20% smaller than the ideal limit. The relationship of the observed disruption precursor with the computed global mode will also be discussed. Stability of the plasma is enhanced by reduced shear reversal and pressure peakedness, indicating possible avenues for the optimization of NCS operations.« less

Authors:
; ;  [1]
  1. General Atomics, San Diego, CA (United States); and others
Publication Date:
OSTI Identifier:
489516
Report Number(s):
CONF-960354-
TRN: 97:011663
DOE Contract Number:  
FG03-95ER54309; W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: International Sherwood fusion theory conference, Philadelphia, PA (United States), 18-20 Mar 1996; Other Information: PBD: 1996; Related Information: Is Part Of 1996 international Sherwood fusion theory conference; PB: 244 p.
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; DOUBLET-3 DEVICE; PLASMA INSTABILITY; PLASMA DISRUPTION; PRESSURE DEPENDENCE; MHD EQUILIBRIUM; SHEAR; ELECTRIC CONDUCTIVITY

Citation Formats

Chu, M S, Greene, J M, and Lao, L L. Resistive instabilities in negative central shear tokamaks with peaked pressure profiles. United States: N. p., 1996. Web.
Chu, M S, Greene, J M, & Lao, L L. Resistive instabilities in negative central shear tokamaks with peaked pressure profiles. United States.
Chu, M S, Greene, J M, and Lao, L L. 1996. "Resistive instabilities in negative central shear tokamaks with peaked pressure profiles". United States.
@article{osti_489516,
title = {Resistive instabilities in negative central shear tokamaks with peaked pressure profiles},
author = {Chu, M S and Greene, J M and Lao, L L},
abstractNote = {The resistive (n = 1) instabilities in negative central shear (NCS) advanced tokamaks with peaked pressure profiles axe investigated systematically by using the MARS resistive MHD code. Two characteristically different types of resistive modes are found. One localized to the inner of the two mode rational surfaces and the other more global. The localized mode is destabilized by shear reversal and plasma pressure peaking. The mode structure has an interchange parity and corresponds to the predicted localized resistive interchange mode when the resistive interchange stability criterion is violated locally (D{sub R} > 0). In a rotating plasma, this mode rotates with the inner rational surface. The global mode has structure corresponding to the coupling of a double pitched mode with an external kink. This mode usually rotates with the outer portion of the plasma. It is destabilized by plasma beta and stabilized by wall and rotation shear. Experimentally, MHD bursts localized on the inside rational q surfaces in NCS discharges were detected prior to disruption in DIII-D. The {beta}{sub N} value at disruption has been found to be independent of q{sub min} and also decreases with p(0)/(p) in quantitative agreement with the predictions of resistive MHD theory; this constitutes the first positive identification of the resistive interchange mode in the tokamak plasma. The resistive {beta} limit is typically 20% smaller than the ideal limit. The relationship of the observed disruption precursor with the computed global mode will also be discussed. Stability of the plasma is enhanced by reduced shear reversal and pressure peakedness, indicating possible avenues for the optimization of NCS operations.},
doi = {},
url = {https://www.osti.gov/biblio/489516}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Dec 31 00:00:00 EST 1996},
month = {Tue Dec 31 00:00:00 EST 1996}
}

Conference:
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