二次电子发射和负离子存在时的鞘层结构特性

Characteristic of plasma sheath in the presence of secondary electron emission and negative ions

建立了包括电子、离子、器壁发射二次电子以及负离子多种成分的等离子体无碰撞鞘层的基本模型,讨论了二次电子发射和负离子对1维稳态等离子体鞘层结构的影响,并且分析了多种成分等离子体鞘层内的二次电子和负离子的相互作用。结果表明:二次电子发射系数的增加和负离子含量的增加,都将导致鞘层的厚度有所减小;二次电子发射系数超过临界发射系数之后,鞘层不再是离子鞘。随着器壁材料二次电子发射系数的增加,鞘层中的负离子密度分布也逐渐增加;负离子的增加,导致二次电子临界发射系数有所增加。另外,在等离子体鞘层中二次电子发射和负离子的存在,也影响着鞘层中电子的放电特性与器壁材料的腐蚀。

The model of the non-collision plasma sheath is developed in the presence of secondary electron emission（SEE） and negative ions. The effect is discussed of the secondary electron emission and negative ions on the sheath of a one-dimensional stationary plasma. The interaction between secondary electrons and negative ions is also analyzed. It is found that the increase of SEE coefficient and negative ion content in the plasma will reduce the width of plasma sheath. If the SEE coefficient is larger than the critical emission coefficient, the sheath would not only formed by ions. In the sheath of a multicomponent plasma, the density of negative ions increases when the SEE coefficient enhances, and the critical SEE coefficient will be bigger with the enhancement of negative ions. In addition, the presence of SEE and negative ions would affect the discharge in the plasma and erosion of the wall.