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Physics of Plasmas -- December 2000 -- Volume 7, Issue 12, pp. 4996-5006

### Numerical study of tilt stability of prolate 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 12 June 2000; accepted 24 August 2000)
Global stability of the field-reversed configuration (FRC) has been investigated numerically using
both three-dimensional magnetohydrodynamic and hybrid (fluid electron and delta-f particle ion) simulations.
The stabilizing effects of velocity shear and finite ion Larmor radius (FLR) on the *n* = 1 internal tilt mode
in the prolate FRCs have been studied. Sheared rotation is found to reduce the growth rate, however a large
rotation rate with Mach number of *M*>~1 is required in order for significant reduction in the instability
growth rate to occur. Kinetic effects associated with large thermal ion orbits have been studied for different
kinetic equilibria. The simulations show that there is a reduction in the tilt mode growth rate due to FLR effects,
but complete linear stability has not been found, even when the thermal ion gyroradius is comparable to the
distance between the field null and the separatrix. The instability existing beyond the FLR theory threshold could
be due to the resonant interaction of the wave with ions whose Doppler shifted frequency matches the betatron
frequency. ©*2000 American Institute of Physics.*

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