The effects of sloshing energetic particles on ballooning modes in tokamaks

Technical Report · Wed Oct 01 04:00:00 EDT 1986

OSTI ID:7250271

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 (approx.0.35 MeV for a tokamak like PDX). Unfortunately, our calculations indicate that the sloshing particles do not have a significant stabilizing effect. An analytic treatment shows that complete stability 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: Texas Univ., Austin (USA). Inst. for Fusion Studies
• DOE Contract Number: FG05-80ET53088
• OSTI ID: 7250271
• Report Number(s): DOE/ET/53088-259; IFSR-259; ON: DE87001932
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700107* -- Fusion Energy-- Plasma Research-- Instabilities
BALLOONING INSTABILITY
CLOSED PLASMA DEVICES
INSTABILITY
PLASMA DRIFT
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
STABILIZATION
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
TRAPPED-PARTICLE INSTABILITY