Parametric investigation for modulation instability of ion wave in negative ion plasma sources

Abstract

The modulational instability of ion acoustic waves in a realistic negative ion source plasma is numerically investigated in this paper. The nonlinear Schrodinger equation describing the modulational instability of ion waves in the presence of negative ions and multispecies positive ions is derived from fluid equations for such plasma system. The average mass of positive ions is found to have a key role in the modulationally unstable ion wave in electronegative plasma. The numerical study of modulational instability of ion waves in such plasma reveals a universal parabolic relationship between the critical density ratio of negative to positive ions and average ionic mass ratio. This relation can be utilized to study the modulational instability experimentally in any realistic negative ion plasma source on a large scale.