Stability analysis of a recently proposed (Svidzinski 2007 Phys. Plasmas14 102512) plasma confinement concept is performed. A separate calculation of the equilibrium profile of the plasma boundary supported by a circularly polarized electromagnetic field is made in collisionless two fluid and kinetic models in slab geometry. In this concept unmagnetized plasma is confined by electromagnetic pressure of the radio frequency (rf) field in toroidal geometry with the confining field frequency in the lower range such that the size of the device is much smaller than the vacuum wavelength. The confining magnetic field is generated by currents in the toroidal shell and by image currents on the plasma surface which are driven by ac voltages applied to toroidal and poloidal gaps in the shell. In the present stability analysis toroidal geometry is approximated by a periodic cylinder, it is assumed that plasma is a perfectly conducting fluid and that there is a vacuum layer between the plasma boundary and conducting shell. In this model a dispersion equation for plasma oscillations near equilibrium is derived. A general stability criterion is calculated when plasma is confined by an elliptically polarized rf field. For an elliptically polarized field stable plasma equilibria can be realized under nonrestrictive conditions for a wide range of ellipticity parameters. In particular, for circular polarization the equilibrium is stable when a ≳ 0.6b, where a is the plasma radius and b is the radius of the cylinder. When plasma is confined by a linearly polarized field its equilibrium is in general unstable. Stable equilibria can also be realized when polarization of the confining field is a superposition of elliptical and linear polarizations. Conclusions about plasma stability under nonrestrictive conditions are expected to be valid in toroidal geometry from the physics consideration of the stabilizing mechanism. The up-to-date studies of the proposed plasma confinement concept indicate that this concept can result in a practical plasma confinement device.
Equilibrium and stability investigations in the belt pinch