Physics of Plasmas -- October 1998 -- Volume 5, Issue 10, pp. 3685-3693

Studies of global stability of field-reversed configuration plasmas using a rigid body model

H. Ji, M. Yamada, R. Kulsrud, N. Pomphrey, and H. Himura
Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543
(Received 22 April 1998; accepted 9 July 1998)

Global stability of field-reversed configuration (FRC) plasmas has been studied using a simple rigid body model in the parameter space of s (the ratio of the separatrix radius to the average ion gyro-radius) and plasma elongation E (the ratio of the separatrix length to the separatrix diameter). Tilt stability is predicted, independent of s, for FRC's with low E (oblate), while the tilt stability of FRC's with large E (prolate) depends on s/E. It is found that plasma rotation due to ion diamagnetic drift can stabilize the tilt mode when s/E<1.7. The so-called collisionless ion gyro-viscosity also is identified to stabilize tilt when s/E<2.2. Combining these two effects, the stability regime broadens to s/E<2.8, consistent with previously developed theories. A small additional rotation (e.g., a Mach number of 0.2) can improve tilt stability significantly at large E. A similar approach is taken to study the physics of the shift stability. It is found that radial shift is unstable when E < 1 while axial shift is unstable when E > 1. However, unlike tilt stability, gyro-viscosity has little effect on shift stability. © 1998 American Institute of Physics.

PACS: 52.55.Ez, 52.35.Py, 52.35.Qz, 52.55.Hc

Full paper: pdf file (241 Kb).