Effect of plasma shaping on performance in the National Spherical Torus Experiment

Journal Article · Mon May 15 00:00:00 EDT 2006 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2198174· OSTI ID:20783147

Gates, D A; Menard, J; Kaye, S; Taylor, G; Wilson, J R; Bell, M G; Bell, R E; Bernabei, S; Biewer, T; Blanchard, W; Darrow, D S; Davis, W; Diem, S; Foley, J; Fredrickson, E D; Hatcher, R E; Hill, K; Hosea, J C; Johnson, D W; Kaita, R ^[1]

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1. Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)

The National Spherical Torus Experiment (NSTX) has explored the effects of shaping on plasma performance as determined by many diverse topics including the stability of global magnetohydrodynamic (MHD) modes (e.g., ideal external kinks and resistive wall modes), edge localized modes (ELMs), bootstrap current drive, divertor flux expansion, and heat transport. Improved shaping capability has been crucial to achieving {beta}{sub t}{approx}40%. Precise plasma shape control has been achieved on NSTX using real-time equilibrium reconstruction. NSTX has simultaneously achieved elongation {kappa}{approx}2.8 and triangularity {delta}{approx}0.8. Ideal MHD theory predicts increased stability at high values of shaping factor S{identical_to}q{sub 95}I{sub p}/(aB{sub t}), which has been observed at large values of the S{approx}37[MA/(m{center_dot}T)] on NSTX. The behavior of ELMs is observed to depend on plasma shape. A description of the ELM regimes attained as shape is varied will be presented. Increased shaping is predicted to increase the bootstrap fraction at fixed I{sub p}. The achievement of strong shaping has enabled operation with 1 s pulses with I{sub p}=1 MA, and for 1.6 s for I{sub p}=700 kA. Analysis of the noninductive current fraction as well as empirical analysis of the achievable plasma pulse length as elongation is varied will be presented. Data are presented showing a reduction in peak divertor heat load due to increasing in flux expansion.

• OSTI ID: 20783147
• Journal Information: Physics of Plasmas, Vol. 13, Issue 5; Other Information: DOI: 10.1063/1.2198174; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BOOTSTRAP CURRENT
BOUNDARY LAYERS
CONTROL
DIVERTORS
EDGE LOCALIZED MODES
ELONGATION
HEAT TRANSFER
HEATING LOAD
KINK INSTABILITY
MAGNETOHYDRODYNAMICS
NSTX DEVICE
PERFORMANCE
PLASMA
PLASMA CONFINEMENT
PULSES
RADIATION TRANSPORT
SPHERICAL CONFIGURATION
STABILITY
WALL EFFECTS