Study of sheath properties in collisional plasma consisting of non-extensive electrons and thermal ions

Abstract

Abstract The main purpose of the present work is to study the behavior of sheath properties in unmagnetized collisional plasma. The plasma consists of neutral atoms, thermal positive ions and non-extensive electrons. The ions are described by fluid model approach, while the electrons are considered following the q-non-extensive distribution and obey the Tsallis statistics. In this study, a steady state one-dimensional fluid model based on the ion continuity and momentum transport equations, in presence of source term, coupled to the Poisson’s equation and non-extensive electrons density equation is developed. The modified Bohm sheath criterion is also determined and studied. The numerical results obtained highlight the effect of the nonextensivity q-parameter and the positive ion temperature on the evolution of the quantities characterizing the plasma sheath, such as charged particles densities, ion velocity, electric potential and sheath thickness. It is seen that as the q-parameter increases, the charged particles densities decrease more rapidly in the sheath region while the normalized electric potential increases strongly, which leads to a significant decrease in sheath thickness. It is also shown that by increasing the ion temperature for constant q, or by increasing the value of q-parameter for constant ion temperature, the ion velocity increases significantly in the sheath.