Numerical study of the effect of secondary electron emission on the sheath characteristics in q‐non‐extensive plasma

Abstract

In this paper, a plasma sheath containing primary electrons, cold positive ions, and secondary electrons is studied using a one-dimensional fluid model in which the primary electrons are described by q-non-extensive distribution according to the Tsallis statistics. Based on the Sagdeev potential method and the current balance relation, a modified sheath criterion, and floating potential are established theoretically. The effect of secondary electron emission on q-non-extensive plasma sheath characteristics have been numerically examined. A significant change is observed in the quantities characterizing the non-extensive plasma sheath with the presence of the secondary electrons. It is found that the sheath properties with super-extensive distribution (q < 1) and sub-extensive distribution (q > 1) are different compared with plasma sheath with Maxwell distribution (q = 1).

Ion flow and dust charging at the sheath boundary in dusty plasma with an electron-emitting surface: applications to laboratory and lunar dusty plasmas

“…The considered physical parameters for collisional plasma are: plasma electron temperature, T pe = 5.5 eV; temperature of emitted electrons from the surface, T ee = 0. r d = 4.0 µm; electron impact ionization frequency for argon gas, g i = 0.048ω pi , where ω pi is the ion plasma frequency; ion loss rate, g a = 0.01 to 0.09ω pi ; gas temperature, T g = 0.0259 eV; and gas pressure, P n = 0.1-30 Pa. We have taken plasma parameters for the weakly coupled laboratory dusty plasma with a coupling parameter less than unity [63]. The plasma parameters taken are consistent with previous experimental and theoretical works [12,29,39,64,65]. The variation of gas pressure affects the electron emission from the surface, and the density distribution of emitted electrons in the sheath region for different values of gas pressure (P n ) is depicted in figure 3.…”

“…For the lunar dusty plasma, the thermal velocity of solar wind positive ions cannot be ignored as it a has dominant contribution close to the sheath boundary. The collection drag force (F coll id ) and the Coulomb drag (F coul id ) due to the thermal speed of positive ions are calculated using equations (38) and (39), respectively.…”

“…They assumed that the plasma electrons obey the Boltzmann relation, whereas the dynamics of emitted electrons is modelled by using fluid equations (momentum and continuity). In recent years, there have been many works devoted to the understanding of sheath formation in front of the electron-emitting surface, but it is still not well understood [29,30,[37][38][39][40][41]. There are several previous works that have explored the sheath characteristics by considering the half-Maxwellian distribution of emitted electrons from the surface.…”

Secondary electron emission and collisional effects in a two‐electron temperature plasma sheath

“…Moreover, expansion of the sheath has also been observed for lower values of $$$ q $$$. Using a non‐extensive electron model, Asserghine et al [ 31 ] have investigated sheath formation in the presence of an electron‐emitting wall. Their study shows that the critical SSE coefficient ($$$ {\gamma}_c $$$) increases for the super‐extensive distribution of electrons ($$$ q<1 $$$) while it decreases for the sub‐extensive electron distribution ($$$ q>1 $$$).…”