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Title: Higher beta at higher elongation in the DIII-D tokamak

Abstract

A theoretical and experimental evaluation of axisymmetric stability and axisymmetric control has led to a modification of the vertical position control in the DIII-D tokamak, which now allows operation to within a few percent of the ideal magnetohydrodynamic (MHD) {ital n}=0 limit. It is found that the onset the departure from rigid shift behavior in D-shaped plasmas limits plasma elongation to 2.5 in DIII-D. The possibility of avoiding the vertical instability in future tokamaks with highly elongated plasmas is discussed. Recent experiments have focused on utilizing this capability for axisymmetric control to construct plasma shapes optimized to increase the achievable beta. Operation near the axisymmetric stability limit allows an increase in the achieved normalized current {ital I}{sub {ital p}}/{ital aB}{sub {ital T}}, where {ital I}{sub {ital p}} is the total plasma current, {ital a} is the minor radius, and {ital B}{sub {ital T}} is the toroidal field. Based on stability calculations, an equilibrium was developed to achieve marginal stability simultaneously to axisymmetric, kink, and ballooning instabilities. In the experiment, the shape was altered to higher elongation during the high-beta phase as the current profile broadened. A record high beta for DIII-D of 11% was achieved. The high-beta phase of themore » discharge lasted 40 msec, approximately one confinement time.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ;  [1]
  1. General Atomics, San Diego, California 92138 (US)
Publication Date:
OSTI Identifier:
5518826
DOE Contract Number:  
AC03-89ER51114; AC05-84OR21400
Resource Type:
Journal Article
Journal Name:
Physics of Fluids B; (USA)
Additional Journal Information:
Journal Volume: 3:8; Journal ID: ISSN 0899-8221
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; HIGH-BETA PLASMA; STABILITY; TOKAMAK DEVICES; OPERATION; BALLOONING INSTABILITY; EQUILIBRIUM; KINK INSTABILITY; MAGNETOHYDRODYNAMICS; OPTIMIZATION; PLASMA MACROINSTABILITIES; SHAPE; CLOSED PLASMA DEVICES; FLUID MECHANICS; HYDRODYNAMICS; INSTABILITY; MECHANICS; PLASMA; PLASMA INSTABILITY; THERMONUCLEAR DEVICES; 700107* - Fusion Energy- Plasma Research- Instabilities

Citation Formats

Lazarus, E A, Chu, M S, Ferron, J R, Helton, F J, Hogan, J T, Kellman, A G, Lao, L L, Lister, J B, Osborne, T H, Snider, R, Strait, E J, Taylor, T S, and Turnbull, A D. Higher beta at higher elongation in the DIII-D tokamak. United States: N. p., 1991. Web. doi:10.1063/1.859639.
Lazarus, E A, Chu, M S, Ferron, J R, Helton, F J, Hogan, J T, Kellman, A G, Lao, L L, Lister, J B, Osborne, T H, Snider, R, Strait, E J, Taylor, T S, & Turnbull, A D. Higher beta at higher elongation in the DIII-D tokamak. United States. doi:10.1063/1.859639.
Lazarus, E A, Chu, M S, Ferron, J R, Helton, F J, Hogan, J T, Kellman, A G, Lao, L L, Lister, J B, Osborne, T H, Snider, R, Strait, E J, Taylor, T S, and Turnbull, A D. Thu . "Higher beta at higher elongation in the DIII-D tokamak". United States. doi:10.1063/1.859639.
@article{osti_5518826,
title = {Higher beta at higher elongation in the DIII-D tokamak},
author = {Lazarus, E A and Chu, M S and Ferron, J R and Helton, F J and Hogan, J T and Kellman, A G and Lao, L L and Lister, J B and Osborne, T H and Snider, R and Strait, E J and Taylor, T S and Turnbull, A D},
abstractNote = {A theoretical and experimental evaluation of axisymmetric stability and axisymmetric control has led to a modification of the vertical position control in the DIII-D tokamak, which now allows operation to within a few percent of the ideal magnetohydrodynamic (MHD) {ital n}=0 limit. It is found that the onset the departure from rigid shift behavior in D-shaped plasmas limits plasma elongation to 2.5 in DIII-D. The possibility of avoiding the vertical instability in future tokamaks with highly elongated plasmas is discussed. Recent experiments have focused on utilizing this capability for axisymmetric control to construct plasma shapes optimized to increase the achievable beta. Operation near the axisymmetric stability limit allows an increase in the achieved normalized current {ital I}{sub {ital p}}/{ital aB}{sub {ital T}}, where {ital I}{sub {ital p}} is the total plasma current, {ital a} is the minor radius, and {ital B}{sub {ital T}} is the toroidal field. Based on stability calculations, an equilibrium was developed to achieve marginal stability simultaneously to axisymmetric, kink, and ballooning instabilities. In the experiment, the shape was altered to higher elongation during the high-beta phase as the current profile broadened. A record high beta for DIII-D of 11% was achieved. The high-beta phase of the discharge lasted 40 msec, approximately one confinement time.},
doi = {10.1063/1.859639},
journal = {Physics of Fluids B; (USA)},
issn = {0899-8221},
number = ,
volume = 3:8,
place = {United States},
year = {1991},
month = {8}
}