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arXiv 0808.2209physics.plasm-ph
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如何在微重力下的尘埃等离子体中制造大的无空隙尘埃团

How to make large, void free dust clusters in dusty plasma under microgravity

V. Land, W. J. Goedheer

摘要:

浸没在等离子体中的微米级固体颗粒的集合被用来模拟固态和流体物理学中的许多系统,这是由于它们的强静电相互作用,它们的大惯性,以及它们足够大以用普通光学观察的事实。在地球上,重力将所谓的尘埃等离子体系统限制在薄的二维层中,除非使用特殊的实验几何结构,包括加热或冷却的电子,和/或使用介电材料。在微重力实验中,无尘空隙的形成打破了三维尘埃等离子体系统的各向同性。为了进行真正的三维实验,这个空洞必须以某种方式关闭。本文利用完全自洽流体模型,研究了微重力实验中通过降低驱动势来封闭空洞的问题。这种分析超越了对虚空的简单描述,虚空描述了虚空的形成,而没有考虑灰尘。我们发现,自组织在空隙形成和空隙闭合中起着重要的作用,这也允许一个相反的方案,其中放电是在低驱动电位和小批量的灰尘被添加。这种方式没有发现滞后现象。最后,我们将我们的结果与最近的实验进行比较,发现很好的一致性,但只有当我们不考虑电荷交换碰撞。

英文摘要:

Collections of micrometer sized solid particles immersed in plamsa are used to mimic many systems from solid state and fluid physics, due to their strong electrostatic interaction, their large inertia, and the fact that they are large enough to be visualized with ordinary optics. On Earth, gravity restricts the so called dusty plasma systems to thin, two-dimensional layers, unless special experimental geometries are used, involving heated or cooled electrons, and/or the use of dielectric materials.In micro-gravity experiments, the formation of a dust-free void breaks the isotropy of three-dimensional dusty plasma systems. In order to do real three-dimensional experiments, this void has somehow to be closed. In this paper, we use a fully self-consistent fluid model to study the closure of a void in a micro-gravity experiment, by lowering the driving potential. The analysis goes beyond the simple description of the virtual void, which describes the formation of a void without taking the dust into account. We show that self-organization plays an important role in void formation and void closure, which also allows a reversed scheme, where a discharge is run at low driving potentials and small batches of dust are added. No hysteresis is found this way. Finally, we compare our results to recent experiments and find good agreement,but only when we do not take charge-exchange collisions into account.

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