Bohm sheath criterion for electronegative warm plasma carrying seconadary electron emission in an oblique magnetic field

The Bohm sheath criterion is formulated by using Sagdeev potential approach for electronegative warm plasma under oblique magnetic field and secondary electron emission from the wall. In this model the effect of collisions between positive ions and neutral, ionization, electronegativity, non-extensivity and temperature ratio (positive/negative ion to electron) are also considered to get the exact behavior of velocity of positive ions at the edge of the sheath. Results are compared with the cases of collision-less, ionization-less and absence of electron emission from the wall and it is found that the Bohm velocity for this case is decreased faster with the increase of non-extensivity and the angle of inclination of the applied magnetic field. Also, Bohm velocity gets increased when the electric field at the edge of the sheath increases. Although Bohm velocity does not depend on the strength of the magnetic field, but the slope in the electrostatic potential gets increased and the sheath thickness decreased on raising the strength of the magnetic field.

Keywords:

Bohm velocity , Electronegative plasma , oblique magnetic field , secondary electrons