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

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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.