Destabilization of MHD modes with finite Larmor radius effects in tandem mirrors

Technical Report · Wed Jan 01 04:00:00 EST 1986

OSTI ID:6284130

Kotschenreuther, M; Berk, H L

Difficulties in the stabilization of ideal magnetohydrodynamic (MHD) ballooning modes by finite Larmor radius (FLR) effects are considered, in tandem mirror geometry for azimuthal mode numbers l > 1. A kinetic formalism is used to obtain corrections to the long thin approximation, when keeping terms of quadratic order in the curvature. If eta/sub i/ = par. deltalnT/sub i/par. deltalnn/sub i/ greater than or equal to 0, with T/sub i/, n/sub i/, the ion temperature and density, ion resonance effects eliminate absolute FLR stability, though the residual growth rates are substantially reduced from the MHD values. Even lowest order FLR stability is difficult to achieve with choke coils present, but is possible with a more gradually tapered mirror. However, the residual modes are still important, and mixing length estimates of the confinement degradation from modes with l > 1 indicate they can still severely limit the achievement of reactor-grade operation near and above the threshold beta value predicted from the ideal MHD theory. This is most severe if the ion temperature gradient decreases radial (eta/sub i/ > 0), whereupon significant instabilities can even arise below the ideal threshold. However, if the ion temperature gradient can be made positive, and -eta/sub i/ < 2/3, the lowest order FLR theory suffices to produce stability. 9 refs., 1 fig.

• Research Organization: Texas Univ., Austin (USA). Inst. for Fusion Studies
• DOE Contract Number: FG05-80ET53088
• OSTI ID: 6284130
• Report Number(s): DOE/ET/53088-219; IFSR-219; ON: DE86005401
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700107* -- Fusion Energy-- Plasma Research-- Instabilities
BALLOONING INSTABILITY
DISPERSION RELATIONS
EIKONAL APPROXIMATION
FLUID MECHANICS
HYDRODYNAMICS
INSTABILITY
LARMOR RADIUS
MAGNETIC MIRRORS
MAGNETOHYDRODYNAMICS
MECHANICS
OPEN PLASMA DEVICES
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
TANDEM MIRRORS
TEMPERATURE GRADIENTS
THERMONUCLEAR DEVICES