Suppression of Ion-Ion Instabilities Excited by an Obliquely Injected Ion Beam

Abstract

An ion beam which is inclined about 70 degrees from the direction of wave propagation is injected into plasmas to excite the ion-ion instability. When the ion beam is modulated by an external RF field, the instability is suppressed and the growth or damping rate changes from that without modulation. In particular, it is found from these results that when the modulation frequency is near the ion plasma frequency f_pi, the growth or damping rate changes markedly. Furthermore, it is observed that a peak in the energy distribution function of the ion beam splits into two peaks when the modulation frequency is near f_pi.