Sheath and boundary conditions in a collisional magnetized warm electronegative plasma

Abstract

The characteristics of a weakly collisional sheath in a warm electronegative plasma in the presence of an oblique magnetic field are investigated using a fluid model including the effects of ionization and ion-neutral collisions. The general sheath criterion imposed on the entrance velocity component of the positive ions perpendicular to the wall at the sheath-presheath edge is derived and discussed. It is shown that the boundary conditions are crucial to the sheath structure. Without including the entrance velocity components parallel to the wall, a pulse-like structure in the positive-ion density distribution near the sheath-presheath edge appears if the magnetic field is strong. With inclusion of all velocity components at the edge, the pulse-like structure disappears, resulting in a smooth sheath profile. It is also found that increasing the temperature and decreasing the concentration of the negative ions will increase the sheath thickness, and increasing the magnetic field will decrease the sheath thickness.

Magnetized plasma sheath in the presence of negative ions

“…On the contrary, the electric force now accelerates the ions toward the wall. 38 With the increase in electronegativity, the electric force is seen to decrease. This decrease in electric force lowers the charge separation, which further increases the particle density in the sheath and, therefore, increases the sheath width.…”

Particle-in-cell simulation of the head-on collision between two ion acoustic solitary waves in plasmas

“…[22][23][24] They have been studied intensively in a broad range of physical problems related to space and laboratory plasmas both theoretically and experimentally. [25][26][27][28] Till now, lots of approaches have been applied to investigate the nature and characteristics of nonlinear structures, [29][30][31][32] while the behaviors shown under the interaction are considered to be very important sources of information. [33][34][35] For the very reason, the collision of two nonlinear waves is a subject of great interest.…”

Sheath properties in active magnetized multi-component plasmas

“…Figure 1 shows the effect of the magnetic field on the density distribution of the charged particles (electron, positive ion and negative ion) in an active and quiescent plasma for γ 1 = 3 , α = 0.01 , τ p1 = 0.1 , δ n1 = 0.5 , τ n1 = 0.1 , θ = 30 • and different values of magnetic field (via ρ ), respectively 6,8,28,[33][34][35][36] . This figure indicates that density distribution of the charged particles and also the sheath width in both active and quiescent plasma increase in the presence of a constant magnetic field which is in agreement with the result of Ref.…”

“…In the present paper, we extend the results of the previous works (for example, Refs. 11,[18][19][20][25][26][27][28][29][30] ) to include an oblique external magnetic field, ion-neutral collision and electron impact ionization as well as multi-charged positive and negative ion species and find analytically the sheath formation criterion in a magnetized multicomponent plasma with ion source term (active plasma) consisting of multi-charged positive and negative ion species. In order to do this, we use a fluid model of plasma and analyze the Sagdeev potential.…”