The effect of collisions, ionisation and non-extensivity is studied numerically in an electronegative warm plasma associated with electron emission from the wall. Electrostatic potential, space charge density, net negative charge density and emitted electron beam density are plotted with the normalised distance to see the effects of aforesaid parameters The negative ion is described with fluid equations to see it’s effect of the mass ratio (negative ion to positive ion) on emitted electron beam density inside the sheath. The three types of electronegative plasma taken are CF_4, O_2 and C_60. The emitted beam electron density is more in number at the wall for higher collisional and ionisation case and less in higher mass ratio. For super-extensive case the emitted beam electrons is lesser than compared to the Boltzmann distributed electrons. The sheath thickness is found to be more in higher mass ratio, emitted beam electrons and super -extensive case while for higher collisional and ionisation case the sheath thickness is less. پرونده مقاله

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. پرونده مقاله