On the space-charge formation in a collisional magnetized electronegative plasma

Abstract

The plasma sheath formation in the vicinity of a surrounding wall of magnetized plasma is studied in the presence of the electronegative ions and the positive ion-neutral background collisions. Fluid equations are used to treat the plasma particles species. By using the Sagdeev potential, the influence of the collisions and the magnetic field on the Bohm criterion are investigated. The space-charge profiles are obtained in the presence of a magnetic field in different collision frequencies as well as electronegative ions concentration. It is shown that the collision and the magnetic field raise a space-charge peak, while the presence of the electronegative ions results in damping the peaks. Moreover, it is observed that in the case of high magnetic field, some fluctuations emerge in the space-charge profiles. The influences of the magnetic field and electronegative ion concentration as well as negative ion temperature on the positive ion kinetic energy reaching the plasma surrounding wall and positive ion velocity perpendicular to the sheath axis are investigated. Finally, the net current through the sheath region is obtained for different collisionality and magnetic field values in both electropositive and electronegative plasmas.