Modified Bohm Criterion and Sheath Characteristics in Nonextensive Electronegative Collisional Warm Plasma With Electron Emitting Surfaces

Abstract

Bohm criterion and sheath formation mechanism are evaluated using Sagdeev potential approach in warm electronegative collisional plasma in contact with electron emitting surfaces and having q-nonextensively distributed electrons. The Bohm velocity is found to depend on the collisional parameter, electron-to-positive-ion temperature ratio, electronegativity, and current density of beam electron emitting from the wall. For different values of these parameters, electric potential, velocity of positive ions, density profile of charged species, and distribution of space charge are also found to vary inside the sheath. The values of Bohm velocity and sheath thickness are found to reduce for the higher collisions and electronegativity, while both these are found to increase with the increase of beam electron current density. The role of nonextensivity is uncovered in the sheath formation by discussing cases with different extents of electronegativity. For the case of low electronegativity, decreasing the nonextensive parameter (q) increases the sheath thickness more significantly as compared to that of the high electronegativity.