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Internal transport barriers in the National Spherical Torus Experimenta)
a)Paper TI2 5, Bull. Am. Phys. Soc. 53, 241 (2008).
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10.1063/1.3129163
/content/aip/journal/pop/16/5/10.1063/1.3129163
http://aip.metastore.ingenta.com/content/aip/journal/pop/16/5/10.1063/1.3129163
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Time evolution of an initially strongly reversed shear plasma displaying an e-ITB until the current redistribution event shown by the MHD trace. (a) Plasma current and heating waveforms, (b) core electron and ion temperatures, (c) elevated indicates reversed shear conditions, and (d) MHD activity. Dashed lines in (a) correspond to times in Fig. 2.

Image of FIG. 2.
FIG. 2.

(a) and (b) current density profiles during and after the reversed shear period.

Image of FIG. 3.
FIG. 3.

Kinetic profiles of an ITB. Using the left hand axes are (a) (b) electron density, (c) electron temperature, (d) ion temperature , and (e) toroidal velocity . Using the right hand axes are (a) magnetic shear, and [(b)–(e)] the normalized inverse gradient scale lengths. Vertical dashed lines indicate radial positions of interest for , , and peak normalized inverse gradient scale lengths.

Image of FIG. 4.
FIG. 4.

Distribution of radial separation between and (a) , for all profiles and e-ITB profiles, (b) the e-ITB (c) the i-ITB. Positive separations indicate that occurs radially further outboard.

Image of FIG. 5.
FIG. 5.

Distribution of values at (a) the e-ITBs, (b) the i-ITBs.

Image of FIG. 6.
FIG. 6.

Peak normalized inverse ITG scale lengths vs peak normalized inverse velocity gradient scale lengths .

Image of FIG. 7.
FIG. 7.

(a) Radius of the i-ITB compared to the location of maximum shear, shown with equality line. (b) Histogram of radial separation between i-ITB and location of maxium positive values indicate i-ITB is radially outwards.

Image of FIG. 8.
FIG. 8.

(a) Radius of the e-ITB vs radius of . (b) Histogram of radial separation between and the e-ITB and i-ITBs. Positive values indicate ITB is radially outwards from .

Image of FIG. 9.
FIG. 9.

Value of minimum magnetic shear vs peak electron temperature gradient. Shaded region in the upper left shows an inaccessible region due to stiff profiles. Horizontal bands show critical ETG gradients calculated using linear GS2 and GYRO simulations. Gray vertical band at serve as a reference from high -mode discharges.

Image of FIG. 10.
FIG. 10.

TRANSP calculations of the electron and ion thermal diffusivities with an ITB. Magnetic axis (not shown) is at 102 cm and the plasma edge is at 154 cm.

Image of FIG. 11.
FIG. 11.

(a) High- microwave scattering fluctuation power spectra comparison between a case with an e-ITB and strongly negative magnetic shear vs a weakly reversed shear case with lower electron temperature gradients. (b) Electron temperatures and (c) -profiles for cases shown in (a), shaded region indicates the high- measurement region.

Image of FIG. 12.
FIG. 12.

(a) High- fluctuation power spectra comparing two rf heated cases, a reversed shear e-ITB case, and a zero shear case. (b) Electron temperatures and (c) -profiles for cases shown in (a), shaded region indicates the high- measurement region.

Image of FIG. 13.
FIG. 13.

(a) at the high- measurement region (b) shearing rate at the high- measurement region.

Image of FIG. 14.
FIG. 14.

Integrated high- power statistics at two ranges of vs the local at the fluctuation measurement location. variation is due to changes in at the measurement location.

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2009-05-20
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Internal transport barriers in the National Spherical Torus Experimenta)
http://aip.metastore.ingenta.com/content/aip/journal/pop/16/5/10.1063/1.3129163
10.1063/1.3129163
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