Theoretical Investigations of Gyrating Ion Beam-Driven Ion-Acoustic Wave Instability in Plasma Using First Order Perturbation Theory

A Gyrating ion beam traveling through a plasma cylinder comprising of electrons, positive ions K+, and heavy C7F14− negative ions, through Cerenkov interaction, drive IAWs (ion-acoustic waves) to unstable mode. In this process, two ion-acoustic (IA) unstable wave modes: a fast K+ mode and a slow C7F14− mode in the presence of positive and heavy negative ions are observed in the plasma. Numerical calculations of the sound wave phase velocity, unstable mode frequency, and the growth rates have been carried out. The calculations show that the growth rate and unstable wave frequencies for both the IA wave modes increase with the increase in the relative density of used heavy negative ions. Moreover, the growth rate is measured as 1/3rd of ion beam density power and the phase velocity rises with the concentration of heavy negative ions. There is a considerable effect of an increase in the magnetic field on the growth rate. The growth rate of the fast (K+) mode increases with the magnetic field more rapidly as compared to the slow ion mode C7F14−.