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Title: Optimization of negative central shear discharges in shaped cross sections

Optimization of negative central shear discharges in shaped cross sections Magnetohydrodynamic (MHD) stability analyses of Negative Central Shear (NCS) equilibria have revealed a new understanding of the limiting MHD instabilities in NCS experiments. Ideal stability calculations show a synergistic effect between cross section shape and pressure profile optimization; strong shaping and broader pressure independently lead to moderately higher {Beta} limits, but broadening of the pressure profile in a strongly dee-shaped cross- section leads to a dramatic increase in the ideal {Beta} limit. Localized resistive interchange (RI) modes can be unstable in the negative shear region and are most restrictive for peaked pressure profiles. Resistive global modes can also be destabilized significantly below the ideal P limit. Experiments largely confirm the general trends, and diagnostic measurements and numerical stability calculations are found to be in good qualitative agreement. Observed disruptions in NCS discharges with L-mode edge and strongly peaked pressure, appear to be initiated by interactions between the RI, and the global ideal and resistive modes.
Authors: ; ; ; ;
Publication Date:
OSTI Identifier:455543
Report Number(s):GA-A--22482; CONF-950956--6
ON: DE97003829; TRN: 97:011988
DOE Contract Number:AC03-89ER51114;FG03-95ER54294;FG05-88ER53266;W-7405-ENG-48
Resource Type:Conference
Data Type:
Resource Relation:Conference: 16. IEEE/NPSS symposium on fusion engineering, Champaign, IL (United States), 30 Sep - 5 Oct 1995; Other Information: PBD: Oct 1996
Research Org:General Atomics, San Diego, CA (United States)
Sponsoring Org:USDOE Office of Energy Research, Washington, DC (United States)
Country of Publication:United States
Language:English
Subject: 70 PLASMA PHYSICS AND FUSION; TOKAMAK DEVICES; PLASMA INSTABILITY; SHEAR; MAGNETOHYDRODYNAMICS; BETA RATIO; PLASMA DISRUPTION; DOUBLET-3 DEVICE; OPTIMIZATION