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Simulation Study on the Dynamics of Dusty Plasmas and the Structure Formation

尘埃等离子体动力学及结构形成的模拟研究

基本信息

批准号：
07680519
负责人：
WATANABE Kunihiko
金额：
$ 1.22万
依托单位：
National Institute for Fusion Science
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07680519/
关键词：
Dusty Plasma Self-organization Simulation Ordered-structure Charging Process Crystalization Dust Grain Coagulation

项目摘要

We have developed a new particle simulation code for dust grains which are dynamically charged by the background plasma. Here, not only the regular attachment effect of the electrons and ions, but also the effects of the secondary electron emission and the coagulation of grains are taken into account.Simulation results show that the all the grains change their charge randomly from negative to positive, or positive to negative in the way of "flio-flop" as the time passes by. The lowest (negative) charge is determined by the balance between the attachment of the electrons and ions, while the highest (positive) charge is determined by the balance between the electron attachment and the secondary electron emission.From the simulation results of various paramenters, it is found that the flip-flop effect is outstanding when the radius of the grains is of the order of 10nm. This is because the attachment of single electron to the grain does not affect much on the surface potential when the ra … More dius of the grain is large enough, say, of the order of the 1 mum. When the radius is small enough, the average probability of the electron attachment becomes small.This fact leads to the another interesting result, namely, the coagulation of a large number of grains, e.g., 1000 grains, make the grain size 10 times larger, so that the flip-flop effect dose not play a major role and grain charge may stay negative.Since the secondary electron emission effect plays a significant role in this simulation, the precise treatment for it is quite important. The secondary electron emission effect would be enhanced more than that given by Sternglas which was employed here, when the grain size is of the order of 10 nm as is treated here.If this enhancement is taken into account, the flip-flop effect shown in the present work becomes more active, even for the larger value of the threshold energy which is assumed here to be a little smaller than the actual one.The dust grains, which are charged in positive or negative, show the coagulation to become larger in size. Because of the above characteristics of the flip-flop effect in the grain size, there exists a probable size of the grains for coagulation. Under the typical parameters of a dust plasma, the most suitable size for the coagulation is found to be of the order of 10nm, which shows a good agreement with the experimental facts. Less

我们已经开发了一个新的粒子模拟程序的尘埃颗粒的动态充电的背景等离子体。模拟中不仅考虑了电子和离子的规则附着效应，还考虑了二次电子发射效应和颗粒凝聚效应，模拟结果表明，随着时间的推移，所有颗粒的电荷都以“触发器”的方式随机地由负变正或由正变负。最低电荷（负电荷）由电子与离子的吸附平衡决定，最高电荷（正电荷）由电子与二次电子的吸附平衡决定，从各种参数的模拟结果可以看出，当晶粒半径为10nm时，这种翻转效应最为显著。这是因为当颗粒表面的电子浓度较低时，颗粒表面的单电子吸附对表面电位的影响不大 ...更多信息晶粒的直径足够大，例如1 μ m的量级。当半径足够小时，电子附着的平均概率变小，这一事实导致另一个有趣的结果，即，大量颗粒的凝聚，例如，1000个晶粒，使晶粒尺寸增大10倍，使触发器效应不起主要作用，晶粒电荷可能保持为负。由于二次电子发射效应在该模拟中起重要作用，因此对其的精确处理是相当重要的。当颗粒尺寸为10 nm量级时，二次电子发射效应比Sternelton给出的结果增强，如果考虑这种增强，则即使在较大的阈值能量（这里假定的阈值能量比实际值稍小）下，触发效应也变得更加活跃。其带正电或负电，显示凝结物尺寸变大。由于上述颗粒尺寸的触发效应的特征，存在用于凝聚的颗粒的可能尺寸。在尘埃等离子体的典型参数下，发现凝聚的最佳尺寸为10nm量级，这与实验事实吻合得很好。少