Magnetized electronegative plasma presheath-sheath containing two positive ion species

The structure of the presheath-sheath for a magnetized electronegative discharge in the presence of two species of positive ions is investigated. In the absence of collision, for different magnetic field strength, the densities of the charges and the profiles of the positive ions velocities and electric potentials are obtained. It is shown that a slightly magnetized uniform structure discharge converts to a stratified multiple layer oscillatory structure for an intermediate magnetic field. But, in contrast to a single positive ion species up to high values of magnetic field, oscillatory behavior continues to exist. We also observe oscillations in the profile of electron densities which are hidden in the single positive ion species case. A competition between the two positive ions species exists which depends on their different masses. The density profiles of the species follow each other along the sheath and the heavier component always occupies higher density values. The influence of the elastic collisions between positive ions and neutrals on the structure of a magnetized electronegative discharge is also investigated. Finally, the positive ion flux at the plasma-sheath edge for each species is obtained as a function of magnetic field strength, for different values of the collision frequency. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3690101]