Suppression, by ion beams, of the m = 2 rotational instability in a field reversed configuration

A hybrid particle simulation shows that the m = 2 rotational instability in a field reversed configuration may be suppressed by ion beams which follow a betatron motion across the field null surface. The energy of the beam ions which contribute to the stabilization is comparable to or a little higher than the field plasma ions, and the averaged beam density needed for the suppression is as low as 1 × 1019 m−3. The mechanism of stabilization due to the ion beams is elucidated by using a simple physical model including the effects of a change of beam orbits caused by the onset of the instability.