碰撞参数对磁化电负性等离子体鞘层结构的影响  

Effect of collision parameter on magnetized electronegative plasma sheath structure

作　　者：刘惠平[1,2] 邹秀[2] 邹滨雁[2] 邱明辉[2] Liu Hui-Ping Zou Xiu Zou Bin-Yan Qiu Ming-Hui(School of Materials Science and Engineering, Dalian Jiaotong University, Dalian 116028, China School of Science, Dalian Jiaotong University, Dalian 116028, China)

机构地区：[1]大连交通大学材料科学与工程学院,大连116028 [2]大连交通大学理学院,大连116028

出　　处：《物理学报》2016年第24期133-138,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:10605008;51372026)资助的课题~~

摘　　要：数值研究了离子马赫数的取值和碰撞参数对由热电子、热负离子和冷正离子构成的磁化电负性等离子体鞘层结构的影响.通过理论推导得到了鞘层模型的玻姆判据的表达式,并得到了不同离子马赫数情况下鞘层的正离子密度分布和净电荷分布曲线,还进一步得到了几个不同碰撞参数下鞘层的带电粒子密度、净电荷以及电势分布曲线.结果表明:离子马赫数取值不同对应不同的鞘层结构;碰撞使鞘层中正离子密度增加,使电子密度更快减小到零,对负离子密度分布影响不明显;碰撞使净电荷密度的峰值幅度增加并向鞘层边缘移动,使鞘层中电势值升高并使鞘层厚度减小.The structure of an electronegative plasma sheath in an oblique magnetic field is investigated.Moreover,the collisions between positive ions and neutral particles are taken into account.It is assumed that the system consists of hot electrons,hot negative ions,and cold positive ions.Also the negative ions and the electrons are assumed to be described by the Boltzmann distributions of their own temperatures,and the accelerated positive ions are treated by the continuity and momentum balance equations through the sheath region.In addition,it is assumed that the collision cross section has a power law dependence on the positive velocity.After theoretical derivation,an exact expression of sheath criterion is obtained.The numerical simulation results include the density distributions of the positive ions for different invariable ion Mach numbers satisfying Bohm criterion,and the comparison of net space charge distribution between variable and invariable ion Mach numbers.Furthermore,three kinds of charged particle densities,the net space charges,and the spatial electric potentials in the sheath are studied numerically for different collision parameters under the condition of the fixed ion Mach number.The results show that the ion Mach number has not only the lower limit but also the upper limit.The ion Mach number affects the sheath structure by influencing the distribution of the positive ion density,and different conclusions can be obtained because ion Mach number is adopted as variable or invariable value when discussing the effects of the other variables which can result in a variety of the ion Mach numbers on the sheath formation.The reason is that the actual sheath structure modification brought on by the variation of a parameter can be divided into two parts.One is the sheath formation change caused directly by the variation of the parameter,and the other is the sheath formation change caused by the Bohm criterion modification which the variation of the parameter results in.Therefore,an identical ion Mach number

关 键 词：鞘层结构 电负性 碰撞 磁场 

分 类 号：O53[理学—等离子体物理]