Centrifugal separation of ions and an oppositely charged non-neutral plasma

The motion of a single ion confined in a Penning-Malmberg trap together with a plasma column of electrons or positrons is described by means of a simple model. The model qualitatively reproduces the basic mechanism of the centrifugal separation for multispecies plasma composed of particles with the same sign of charge. The ion is pushed toward the plasma boundary also when its charge and the plasma charge have opposite signs. An estimation of the characteristic time scale for the separation is obtained and discussed