3-D MHD stability of high-beta free-boundary tokamak plasmas with finite edge-pressure-gradient and limiter stabilization

Conference · Wed Feb 01 04:00:00 EST 1984

OSTI ID:6912018

Lee, J K; Bernard, L C; Chu, M S; Moore, R W; Ohyabu, N

Ideal and resistive external kink-tearing-ballooning modes are studied for high-beta toroidal tokamak plasmas with a varying pedestal and/or with stabilization due to a limiter. When the pedestal value is small, the mode spectrum peaks near n=1 with a monotonically decreasing growth rate in n, in which case the most unstable mode has a structure similar to an ideal external kink mode. As the pedestal value increases, the linear growth rate decreases for a fixed beta and the mode spectrum tends to broaden. The perturbation becomes localized near the plasma edge resembling the edge relaxation phenomenon in an H-mode tokamak discharge. The stabilizing effect of a limiter on high-beta MHD modes is considered for a finite-size toroidal limiter, a poloidal limiter, and a general limiter. For the latter two types of limiters, a 3-D linear stability analysis is necessary, coupling both poloidal and toroidal modes. The high-beta toroidal case has different characteristics from the zero-beta cyclindrical case; among them is a substantial reduction in growth rate even with modest contact area. Optimum position and size of a limiter are found through extensive parameter studies. A scheme to stabilize the high-beta external kink-tearing mode by means of a set of passive feedback coils is also discussed.

• Research Organization: GA Technologies, Inc., San Diego, CA (USA)
• DOE Contract Number: AT03-84ER53158
• OSTI ID: 6912018
• Report Number(s): GA-A-17483; CONF-840616-1; ON: DE84009188
• 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
HIGH-BETA PLASMA
INSTABILITY
INSTABILITY GROWTH RATES
KINK INSTABILITY
LIMITERS
PLASMA
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
TEARING INSTABILITY
THERMONUCLEAR DEVICES
THREE-DIMENSIONAL CALCULATIONS
TOKAMAK DEVICES