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Edge radial electric field structure and its connections to -mode confinement in Alcator C-Mod plasmasa)
a)Paper NI1 2, Bull. Am. Phys. Soc. , 159 (2008).
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10.1063/1.3080721
/content/aip/journal/pop/16/5/10.1063/1.3080721
http://aip.metastore.ingenta.com/content/aip/journal/pop/16/5/10.1063/1.3080721
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Simultaneous high-confinement mode profiles of (a) temperature , (b) density , and (c) toroidal and poloidal velocity , from the edge CXRS diagnostic. The solid curves are fits to the data using a modified tanh function defined in Eq. (1) of Ref. 38 . The gray boxes highlight the pedestal region for each parameter. The vertical dashed line indicates the position of the LCFSs.

Image of FIG. 2.
FIG. 2.

Characteristics of a C-Mod EDA -mode. (a) , (b) radiated power, (c) line averaged density, (d) electron temperature, (e) plasma confinement factor H98, (f) magnetic fluctuations, and (g) input ICRH power. The gray highlighted region indicates the -mode portion of the discharge.

Image of FIG. 3.
FIG. 3.

Examples of radial electric field and shear profiles in EDA -modes. (a) forms a deep negative well just inside the LCFS in -mode. (b) The shearing rate frequency is of the order of 3 MHz in the pedestal region. The -mode profiles are shown by the solid black lines. The circle symbols indicate the -mode profiles. The colored profiles (online) are individual time frames.

Image of FIG. 4.
FIG. 4.

Contributions of the three components from Eq. (1) to the radial electric field in an EDA -mode. The poloidal velocity contribution dominates the width of the well.

Image of FIG. 5.
FIG. 5.

Characteristics of a C-Mod ELM-free -mode. (a) , (b) radiated power, (c) line averaged density, (d) electron temperature, (e) plasma confinement factor H98, (f) magnetic fluctuations, and (g) input ICRH power. The gray highlighted regions indicate the -mode portions of the discharge.

Image of FIG. 6.
FIG. 6.

Examples of radial electric field (a) and shear profiles (b) in ELM-free -modes. The depth of the well and the shear frequency decay as the -mode evolves.

Image of FIG. 7.
FIG. 7.

Evolution of all three contributions from Eq. (1) to the radial electric field in an ELM-free -mode. The (a) diamagnetic component, (b) poloidal velocity contribution, and (c) and toroidal velocity contribution all diminish as the ELM-free -mode evolves.

Image of FIG. 8.
FIG. 8.

Comparison of , as measured using ions, to an estimate of the main ion diamagnetic contribution to from the Thomson scattering diagnostic. The main ion diamagnetic estimate can account for most of the shape, depth, and position of the well.

Image of FIG. 9.
FIG. 9.

Main ion perpendicular velocity determined by the difference between the total radial electric field and the estimate of the main ion diamagnetic contribution. The main ions have a significant flow component perpendicular to the total magnetic field in the pedestal region.

Image of FIG. 10.
FIG. 10.

Plasma confinement (H89) vs well depth for EDA and ELM-free -modes. There is a correlation between deeper radial electric field wells and improved plasma energy confinement.

Image of FIG. 11.
FIG. 11.

Edge electron pedestal parameters, (a) , (b) , and (c) as a function of well depth. There is a correlation between deeper radial electric field wells and higher temperature pedestal heights. There is little correlation between and density pedestal heights.

Image of FIG. 12.
FIG. 12.

Radial electric field well widths (FWHM) vs machine major radii collected from the published literature (Refs. 16, 17, 21, and 24 ). The width of the radial electric field well appears to scale, to first order, with machine size.

Image of FIG. 13.
FIG. 13.

Characteristics of a C-Mod -mode plasma. (a) , (b) radiated power, (c) line averaged density, (d) electron temperature, (e) plasma confinement factor H98, (f) magnetic fluctuations, and (g) input ICRH power. The gray highlighted region indicates the -mode portion of the discharge.

Image of FIG. 14.
FIG. 14.

Comparison of (a) edge electron temperature and (b) electron density profiles between -mode, -mode, and -mode plasmas. The -mode temperature profile approaches -mode values, while the -mode density profile remains closer to -mode levels.

Image of FIG. 15.
FIG. 15.

Comparison of (a) the radial electric field and (b) the shear profiles between an -mode, -mode, and EDA -mode. -mode radial electric field well depths and shear rates are lower than their -mode counterparts.

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2009-03-12
2014-04-25
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Edge radial electric field structure and its connections to H-mode confinement in Alcator C-Mod plasmasa)
http://aip.metastore.ingenta.com/content/aip/journal/pop/16/5/10.1063/1.3080721
10.1063/1.3080721
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