Simulation Research on the Growth Process and Dynamics of Grains in Dusty Plasmas

我们开发了能够跟踪尘埃等离子体中颗粒动力学的模拟程序，并研究了颗粒的充电/凝聚过程。取得了以下成果。1)当颗粒尺寸和背景等离子体温度合适时，颗粒由于电子附着而带负电荷，或者由于二次电子或光电子以触发器的方式发射而带正电荷。2)由于尘埃等离子体中同时存在相反电荷的粒子，它们相互吸引和凝聚生长。3)当晶粒尺寸在10 nm左右时，晶粒的生长达到最大。在晶粒度太小或太大的情况下，它们不会生长。4)当考虑光电子发射效应时，颗粒容易以触发器方式带电，从而凝聚长大。因此，在光电子发射效应占主导地位的空间等离子体中可能存在非常大的颗粒。5)成熟的颗粒呈蓝色浆果的形状。这一结果与在加工等离子体中的硅生长实验中观察到的这种颗粒的事实相一致。6)在恒定电场作用下，晶粒生长不均匀。因此，引力场中大部分长大的颗粒可能会发生扭曲。上述结果与实验结果在定性和定量上都有很好的一致性。除了上述仿真研究外，还开发了虚拟现实表达式，以详细研究颗粒的生长过程。在虚拟现实系统中，可以观察到一个颗粒是如何生长成蓝色浆果的形状的。

We have developed the simulation code that can pursue the grain dynamics in dusty plasmas, and investigated the charging/coagulation process of the grains. The following results have been obtained. 1) The grains are charged negatively due to the electron attachment, or positively due to the secondary electron or photo-electron emission in the way of flip-flop when the size of the grains and the background plasma temperature are appropriate. 2) Since there exist oppositely charged grains simultaneously in the dusty plasma, they attract and coagulate with each other to grow. 3) The maximum growth of the grains are realized when the grain size is of the order of 10 nm. In the case that the grain size is too small or too large, they will not grow. 4) When the photo-electron emission effect is taken into account, the grains are easily charged in the flip-flop way, and hence coagulate to grow large. Therefore, there can exist very large grains in the space plasma where the photo-electron emission effect is dominant. 5) The grownup grains show the shape of the blue berry. This result agrees with the fact that such grains were observed in the silicon growth experiment in the processing plasmas. 6) When the stationary electric filed is given, the grains are growing up inhomogeneously. Therefore, the largely grown-up grains in the gravitational filed may become distorted. Above results show a good agreement with the experimental results qualitatively and quantitatively. In addition to above simulation research, the virtual reality expression has been also developed in order to investigate the growing process of the grains in detail. It can be observed in the virtual reality system how one grain grows into the shape of the blue berry.