Studies of feedback stabilization of axisymmetric modes in deformable tokamak plasmas

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1991

OSTI ID:5655284

Ward, D J

A new linear MHD stability code, NOVA-W, is described and applied to the study of the feedback stabilization of the axisymmetric mode in deformable tokamak plasma. The NOVA-W code is a modification of the non-variational MHD stability code NOVA that includes the effects of resistive passive conductors and active feedback circuits. The vacuum calculation has been reformulated in terms of the perturbed poloidal flux to allow the inclusion of perturbed toroidal currents outside the plasma. The boundary condition at the plasma-vacuum interface relates the instability displacement to the perturbed poloidal flux. This allows a solution of the linear MHD stability equations with the feedback effects included. The code has been tested for the case of passive stabilization against a simplified analytic model and against a different numerical calculation for a realistic tokamak configuration. The comparisons demonstrate the accuracy of the NOVA-W results. The NOVA-W code is used to examine the effects of plasma deformability on feedback stabilization. It is seen that plasmas with shaped cross sections have unstable motion different from a rigid shift. Plasma equilibria with large triangularity show particularly significant deviations from a uniform rigid shift. Furthermore, the placement of passive conductors is shown to modify the non-rigid components of the motion in a way that reduces the stabilizing effects of these conductors. The eigenfunction is also modified under the effects of active feedback. This deformation is seen to depend strongly on the position of the flux loops. These non-rigid components of the eigenfunction always serve to reduce the stabilizing effect of the active feedback system by reducing the measurable poloidal flux at the flux-loop locations.

• Research Organization: Princeton Univ., NJ (United States)
• OSTI ID: 5655284
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700430* -- Fusion Technology-- Magnet Coils & Fields-- (1992-)
ACCURACY
BOUNDARY CONDITIONS
CLOSED PLASMA DEVICES
COMPUTER CODES
DEFORMATION
FEEDBACK
INSTABILITY
MAGNETIC FLUX
N CODES
PERFORMANCE
PLASMA
PLASMA INSTABILITY
STABILIZATION
THERMONUCLEAR DEVICES
TOKAMAK DEVICES