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Internal transport barriers in the National Spherical Torus Experiment

Publication ,  Conference
Yuh, HY; Levinton, FM; Bell, RE; Hosea, JC; Kaye, SM; Leblanc, BP; Mazzucato, E; Peterson, JL; Smith, DR; Candy, J; Waltz, RE; Domier, CW ...
Published in: Physics of Plasmas
June 10, 2009

In the National Spherical Torus Experiment [M. Ono, Nucl. Fusion 41, 1435 (2001)], internal transport barriers (ITBs) are observed in reversed (negative) shear discharges where diffusivities for electron and ion thermal channels and momentum are reduced. While neutral beam heating can produce ITBs in both electron and ion channels, high harmonic fast wave heating can also produce electron ITBs (e-ITBs) under reversed magnetic shear conditions without momentum input. Interestingly, the location of the e-ITB does not necessarily match that of the ion ITB (i-ITB). The e-ITB location correlates best with the magnetic shear minima location determined by motional Stark effect constrained equilibria, whereas the i-ITB location better correlates with the location of maximum E×B shearing rate. Measured electron temperature gradients in the e-ITB can exceed critical gradients for the onset of electron thermal gradient microinstabilities calculated by linear gyrokinetic codes. A high- k microwave scattering diagnostic shows locally reduced density fluctuations at wave numbers characteristic of electron turbulence for discharges with strongly negative magnetic shear versus weakly negative or positive magnetic shear. Reductions in fluctuation amplitude are found to be correlated with the local value of magnetic shear. These results are consistent with nonlinear gyrokinetic simulations predicting a reduction in electron turbulence under negative magnetic shear conditions despite exceeding critical gradients. © 2009 American Institute of Physics.

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Published In

Physics of Plasmas

DOI

ISSN

1070-664X

Publication Date

June 10, 2009

Volume

16

Issue

5

Related Subject Headings

  • Fluids & Plasmas
  • 5109 Space sciences
  • 5106 Nuclear and plasma physics
  • 0203 Classical Physics
  • 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics
  • 0201 Astronomical and Space Sciences
 

Citation

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Yuh, H. Y., Levinton, F. M., Bell, R. E., Hosea, J. C., Kaye, S. M., Leblanc, B. P., … Park, H. K. (2009). Internal transport barriers in the National Spherical Torus Experiment. In Physics of Plasmas (Vol. 16). https://doi.org/10.1063/1.3129163
Yuh, H. Y., F. M. Levinton, R. E. Bell, J. C. Hosea, S. M. Kaye, B. P. Leblanc, E. Mazzucato, et al. “Internal transport barriers in the National Spherical Torus Experiment.” In Physics of Plasmas, Vol. 16, 2009. https://doi.org/10.1063/1.3129163.
Yuh HY, Levinton FM, Bell RE, Hosea JC, Kaye SM, Leblanc BP, et al. Internal transport barriers in the National Spherical Torus Experiment. In: Physics of Plasmas. 2009.
Yuh, H. Y., et al. “Internal transport barriers in the National Spherical Torus Experiment.” Physics of Plasmas, vol. 16, no. 5, 2009. Scopus, doi:10.1063/1.3129163.
Yuh HY, Levinton FM, Bell RE, Hosea JC, Kaye SM, Leblanc BP, Mazzucato E, Peterson JL, Smith DR, Candy J, Waltz RE, Domier CW, Luhmann NC, Lee W, Park HK. Internal transport barriers in the National Spherical Torus Experiment. Physics of Plasmas. 2009.

Published In

Physics of Plasmas

DOI

ISSN

1070-664X

Publication Date

June 10, 2009

Volume

16

Issue

5

Related Subject Headings

  • Fluids & Plasmas
  • 5109 Space sciences
  • 5106 Nuclear and plasma physics
  • 0203 Classical Physics
  • 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics
  • 0201 Astronomical and Space Sciences