Advances in measurement and modeling of the high-confinement-mode pedestal on the Alcator C-Mod tokamak

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

DOI:https://doi.org/10.1063/1.2180748· OSTI ID:20783128

Hughes, J W; LaBombard, B; Mossessian, D A; Hubbard, A E; Terry, J; Biewer, T ^[1]

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1. Plasma Science and Fusion Center, Massachusetts Institute of Technology, 175 Albany Street, Cambridge, Massachusetts 02139 (United States)

Edge transport barrier (ETB) studies on the Alcator C-Mod tokamak [Phys. Plasmas 1, 1511 (1994)] investigate pedestal scalings and the radial transport of plasma and neutrals. Pedestal profiles show trends with plasma operational parameters such as total current I{sub P}. A ballooning-like I{sub P}{sup 2} dependence is seen in the pressure gradient, despite calculated stability to ideal ballooning modes. A similar scaling is seen in the near scrape-off layer for both low-confinement (L-mode) and H-mode discharges, possibly due to electromagnetic fluid drift turbulence setting transport near the separatrix. Neutral density diagnosis allows an examination of D{sup 0} fueling in H-modes, yielding profiles of effective particle diffusivity in the ETB, which vary as I{sub P} is changed. Edge neutral transport is studied using a one-dimensional kinetic treatment. In both experiment and modeling, the C-Mod density pedestal exhibits a weakly increasing pedestal density and a nearly invariant density pedestal width as the D{sup 0} source rate increases. Identical modeling performed on pedestal profiles typical of DIII-D [Nucl. Fusion 42, 614 (2002)] reveal differences in pedestal scalings qualitatively similar to experimental results.

• OSTI ID: 20783128
• Journal Information: Physics of Plasmas, Vol. 13, Issue 5; Other Information: DOI: 10.1063/1.2180748; (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
ALCATOR DEVICE
BALLOONING INSTABILITY
COMPUTERIZED SIMULATION
DOUBLET-3 DEVICE
ELECTRIC CURRENTS
FLUIDS
H-MODE PLASMA CONFINEMENT
L-MODE PLASMA CONFINEMENT
PLASMA
PLASMA DENSITY
PLASMA DIAGNOSTICS
PLASMA PRESSURE
PLASMA SCRAPE-OFF LAYER
PLASMA SIMULATION
PRESSURE GRADIENTS
TURBULENCE