Effects of sloshing energetic particles on ballooning modes in tokamaks

Journal Article · Fri May 01 04:00:00 EDT 1987 · Phys. Fluids; (United States)

DOI:https://doi.org/10.1063/1.866256· OSTI ID:6625645

Stotler, D P; Berk, H L

Distributions that give rise to energetic trapped particle pressures peaked in the ''good curvature'' region of a tokamak (sloshing distributions) are examined in an attempt to find stable regimes for both the magnetohydrodynamic (MHD) and precessional modes. It is the precessional drift destabilization of ballooning modes that inhibits bridging the unstable gap to second stability by the use of deeply trapped energetic particles unless the hot particles have an extremely large energy (--0.35 MeV for a tokamak like PDX (Phys. Rev. Lett. 49, 326 (1982))). Unfortunately, our calculations indicate that the sloshing particles do not have a significant stabilizing effect. An analytic treatment shows that stability for the precessional mode can be found only if the sign of the energetic particle magnetic drift frequency can be reversed from its value in vacuum bad curvature without hot species diamagnetism. This is difficult to do in a tokamak because of the destabilizing contribution of the geodesic curvature to the drift frequency. Furthermore, for each of the two sloshing distributions employed (one contains only trapped particles; the other includes trapped and passing particles), a new ''continuum instability'' (where asymptotically along the field line the mode is a propagating plane wave) is found to be driven by geodesic curvature. These results indicate that energetic sloshing particles are not able to bridge the unstable gap to second stability.

• Research Organization: Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712
• OSTI ID: 6625645
• Journal Information: Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 30:5; ISSN PFLDA
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700107* -- Fusion Energy-- Plasma Research-- Instabilities
ANALYTICAL SOLUTION
BALLOONING INSTABILITY
CLOSED PLASMA DEVICES
COUPLING
DIAMAGNETISM
DISTRIBUTION
ELECTRON DRIFT
FLUID MECHANICS
HYDRODYNAMICS
INSTABILITY
MAGNETISM
MAGNETOHYDRODYNAMICS
MECHANICS
PLASMA
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
PRECESSION
RESONANCE
STABILIZATION
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
TRAPPED-PARTICLE INSTABILITY