不同成分等离子体鞘层的玻姆判据

The Bohm criterion of plasma sheath with different species

在一维平板鞘层中采用流体模型分别研究了不同成分无碰撞等离子体鞘层的玻姆判据.通过拟牛顿法数值模拟了含有电子、离子、负离子以及二次电子的等离子体鞘层玻姆判据.结果表明二次电子发射增加了鞘层离子马赫数的临界值,且器壁发射二次电子温度越高,离子马赫数临界值越小.负离子使离子马赫数临界值减小.而在含有二次电子和负离子的等离子体鞘层中,当负离子较少时,二次电子发射对离子马赫数临界值影响较大;当负离子增加时,离子马赫数的临界值则主要受负离子的影响.

A fluid model has been used to study the Bohm criterion of the plasma sheath with different species.The charge particle includes electrons,ions,negative ions and secondary electrons from the wall striked by the electrons.Numerical calculation results are obtained through quasi-Newton method.It is found that secondary electron emission（SEE） can increase the critical ion Mach number of the plasma sheath.The critical ion Mach number decreases with the increase of the temperature of the electrons emitted.Negative ions reduce this critical number.In addition,it is obvious that the SEE affects the ion Mach number when the density of negative ions is small,but the ion Mach number is mainly affected by negative ions when the density of negative ions is high in the presence of secondary electron emission and negative ions.