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Title: Magnetic-divertor stabilization of an axisymmetric plasma with anisotropic temperature

Abstract

Magnetohydrodynamic stabilization of an axisymmetric mirror plasma with a magnetic divertor is studied. An equation is found for the flute modes, which includes the stabilizing influence of ion temperature anisotropy and nonparaxial magnetic fields, as well as a finite ion Larmor radius. It is shown that if the density profile is sufficiently gentle, then the nonparaxial configuration can stabilize all modes as long as ion temperature is radially uniform. This can be demonstrated even when the density vanishes on the separatrix and even for small ion Larmor radii. It is found, however, that the ion temperature gradient makes the unstable region wider; high ion temperature is required to stabilize the flute mode.

Authors:
; ; ; ;  [1];  [2]
  1. Plasma Research Center, University of Tsukuba, Tsukuba, Ibaraki 305-8577 (Japan)
  2. (Russian Federation)
Publication Date:
OSTI Identifier:
20860440
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 13; Journal Issue: 12; Other Information: DOI: 10.1063/1.2402912; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANISOTROPY; AXIAL SYMMETRY; DIVERTORS; ELECTRON TEMPERATURE; FLUTE INSTABILITY; ION TEMPERATURE; LARMOR RADIUS; MAGNETIC FIELDS; MAGNETIC MIRRORS; MAGNETOHYDRODYNAMICS; PLASMA; PLASMA DENSITY; RADIATION TRANSPORT; STABILIZATION; TEMPERATURE GRADIENTS

Citation Formats

Sasagawa, Y., Katanuma, I., Mizoguchi, Y., Cho, T., Pastukhov, V. P., and RRC 'Kurchatov Institute', Kurchatov Square, 1, 123182 Moscow. Magnetic-divertor stabilization of an axisymmetric plasma with anisotropic temperature. United States: N. p., 2006. Web. doi:10.1063/1.2402912.
Sasagawa, Y., Katanuma, I., Mizoguchi, Y., Cho, T., Pastukhov, V. P., & RRC 'Kurchatov Institute', Kurchatov Square, 1, 123182 Moscow. Magnetic-divertor stabilization of an axisymmetric plasma with anisotropic temperature. United States. doi:10.1063/1.2402912.
Sasagawa, Y., Katanuma, I., Mizoguchi, Y., Cho, T., Pastukhov, V. P., and RRC 'Kurchatov Institute', Kurchatov Square, 1, 123182 Moscow. Fri . "Magnetic-divertor stabilization of an axisymmetric plasma with anisotropic temperature". United States. doi:10.1063/1.2402912.
@article{osti_20860440,
title = {Magnetic-divertor stabilization of an axisymmetric plasma with anisotropic temperature},
author = {Sasagawa, Y. and Katanuma, I. and Mizoguchi, Y. and Cho, T. and Pastukhov, V. P. and RRC 'Kurchatov Institute', Kurchatov Square, 1, 123182 Moscow},
abstractNote = {Magnetohydrodynamic stabilization of an axisymmetric mirror plasma with a magnetic divertor is studied. An equation is found for the flute modes, which includes the stabilizing influence of ion temperature anisotropy and nonparaxial magnetic fields, as well as a finite ion Larmor radius. It is shown that if the density profile is sufficiently gentle, then the nonparaxial configuration can stabilize all modes as long as ion temperature is radially uniform. This can be demonstrated even when the density vanishes on the separatrix and even for small ion Larmor radii. It is found, however, that the ion temperature gradient makes the unstable region wider; high ion temperature is required to stabilize the flute mode.},
doi = {10.1063/1.2402912},
journal = {Physics of Plasmas},
number = 12,
volume = 13,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}
  • Passive stabilization, associated with the mutual inductances of the field shaping coils with the plasma and with each other, can stabilize the axisymmetric magnetohydrodynamic instability in the Princeton poloidal divertor experiment device that was observed in earlier numerical studies.
  • A divertor coil set has been installed on the Tara tandem mirror (Nucl. Fusion 22, 549 (1982); Plasma Physics and Controlled Nuclear Fusion Research 1984 (IAEA, Vienna, 1985), Vol. 2, p. 285) for stabilization of m = 1 flutelike modes. The effectiveness of divertor stabilization is discussed in experiments where m = 1 modes are driven to instability by plug electron cyclotron heating (ECH) in an ion cyclotron heated (ICH) plasma. The instability onset is characterized by thresholds in ECH power, fueling rate, ICH power, and mapping radius of the divertor null. In general, the stability is enhanced by mappingmore » the null radially inwards into the plasma. The interdependence of these parameters and their effect on equilibrium profiles and stability boundaries are discussed.« less
  • A pair of two dimensional fast cameras with a wide angle view (allowing a full radial and toroidal coverage of the lower divertor) was installed in the National Spherical Torus Experiment in order to monitor non-axisymmetric effects. A custom polar remapping procedure and an absolute photometric calibration enabled the easier visualization and quantitative analysis of non-axisymmetric plasma material interaction (e.g., strike point splitting due to application of 3D fields and effects of toroidally asymmetric plasma facing components).
  • An axisymmetric divertor has been installed at the central cell midplane of Tara to provide magnetohydrodynamics stability and to generate a high-density halo at the edge of the plasma. A dense halo aids sloshing ion buildup in the plug cells and increases shielding of the core plasma from charge exchange recombination. Separate gas fueling of the halo in the divertor allows for the different fueling requirements of the potential-confined core plasma and the flow-confined edge during plugged operation.