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Physics of Plasmas -- April 2001 -- Volume 8, Issue 4 pp. 1267-1277

### Numerical study of global stability of oblate field-reversed configurations

- E. V. Belova, S. C. Jardin, H. Ji, M. Yamada, and R. Kulsrud
*Princeton Plasma Physics Laboratory, Princeton, New Jersey
08543*

(Received 4 October 2000; accepted 18 January 2001)
Global stability of the oblate (small elongation, E<1) Field-Reversed
Configuration (FRC) has been investigated numerically using both
three-dimensional magnetohydrodynamic (MHD) and hybrid (fluid electrons and
kinetic ions) simulations. For every nonzero value of the toroidal mode
number n, there are three MHD modes that must be stabilized. For n = 1,
these are the interchange, the tilt and the radial shift; while for n>1
these are the interchange and two co-interchange modes with different
polarization. It is shown that the n = 1 tilt mode becomes an external mode
when E<1, and it can be effectively stabilized by close-fitting conducting
shells, even in the small Larmor radii (MHD) regime. The tilt mode stability
improves with increasing oblateness, however at sufficiently small
elongations the radial shift mode becomes more unstable than the tilt mode.
The interchange mode stability is strongly profile dependent, and all n[>=]1
interchange modes can be stabilized for a class of pressure profile with
separatrix beta larger than 0.035. Our results show that all three n = 1
modes can be stabilized in the MHD regime, but the stabilization of the n>1
co-interchange modes still remains an open question.
©*2000 American Institute of Physics.*

**PACS:** 52.35.Py, 52.55.Hc, 52.65.Rr, 52.65.Kj
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