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

本研究的目的是研究库仑晶体在复杂等离子体中的自组织，这将导致的吸引力和排斥力。为了实现这一目标，在2006年实验研究了粒子间距离对各种条件的依赖性。通过2006年的研究，得到了一个新的假设，即粒子间距离是由库仑排斥力和来自等离子体压力的推力（类似于吸引力）之间的平衡决定的。为了证实这一假设，2007年使用了不同直径的颗粒。在直径为1微米和5微米的单分散颗粒的两种情况下，成功地获得了库仑晶体，而没有任何人工的颗粒限制机制。为了研究库仑晶体的自组织机制，首先在不同的气压和射频功率条件下获得晶体的图像。然后，从图像中获得颗粒的坐标。利用这些坐标，得到了对分布函数。此外，还从对分布函数中得到了晶体的配位数。从后面的信息中，可以讨论结构。根据前一信息，获得颗粒间距离。得到了颗粒间距离与颗粒表面电荷的平方与长度之比的关系。在1微米的情况下，2006年发现颗粒间距离与该比率成比例。这就是为什么提出前面的假设的原因。在2007年，在5微米的情况下获得了相同的依赖性。据发现，这种依赖性支持的假设。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.