Investigation on self-organization mechanisms of Coulomb crystal in complex plasmas

本研究的目的是研究复杂等离子体中库仑晶体的自组织，这是由引力和斥力引起的。为了实现这一目标，2006年对粒子间距离在不同条件下的依赖关系进行了实验研究。通过2006年的研究，得到了粒子间距离由库仑斥力和等离子体压力的推力之间的平衡决定的新假设，这与引力类似。为了证实这一假设，2007年使用了不同直径的粒子。在直径分别为1微米和5微米的单分散粒子中，均成功地获得了库仑晶体，而无需任何人工粒子约束机制。为了研究库仑晶体的自组织机制，首先获得了不同气压和射频功率条件下的晶体图像。然后，从图像中得到粒子的坐标。利用坐标，得到了对分布函数。此外，还通过对分布函数得到了晶体的配位数。从后一种信息，可以讨论结构。由前一种信息，得到粒子间距离。得到了粒子间距离与粒子表面电荷与长度的平方之比的关系。在1微米的情况下，2006年发现粒子间距离与该比率成正比。这就是提出前面假设的原因。2007年，在5微米的情况下获得了相同的依赖关系。研究发现，这种依赖关系支持这一假设。与此类似的假设从未被提出过。

The objective of this research is to investigate the self-organization of the Coulomb crystal in complex plasmas, which will be caused by the attractive and repulsive forces. In order to accomplish this objective, dependencies of the inter-parbcle distance on various conditions are experimentally investigated in 2006. Through the research in 2006, a new hypothesis that the inter-particle distance is determined by the balance between the Coulomb repulsive force and the pushing force from the plasma pressure, which is similar to the attractive force, is obtained. In order to confirm this hypothesis, particles with different diameters are used in 2007. In both cases of monodisperse particles with 1 micrometer and 5 micrometers in diameter, the Coulomb crystals are successfully obtained without any artificial particle-confinement mechanisms. In order to investigate the self-organization mechanisms of the Coulomb crystal, the images of the crystals are obtained first under various gas pressure and rf power conditions. Then, the coordinates of the particles are obtained from the images. By using the coordinates, the pair distribution function are obtained. In addition, the coordination number of the crystal is also obtained from the pair distribution function. From the latter information, the structure can be discussed. From the former information, the inter-particle distance is obtained. The dependencies of the inter-particle distance on the ratio of the square of the surface charge of the particte to length are obtained. In the 1 micrometer case, it was found that the inter-particle distance is proportional to that ratio in 2006. This is the reason why the previous hypothesis is proposed. In 2007, the same dependencies in the case of 5 micrometers are obtained. It is found that this dependency supports the hypothesis. The hypothesis being similar to this one has never been proposed.