Melzer A, Nunomura S, Samsonov D, Ma ZW, Goree J
Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242, USA.
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 2000 Sep;62(3 Pt B):4162-76. doi: 10.1103/physreve.62.4162.
Experimental studies of the formation and structure of Mach cones in a plasma crystal are presented. Plasma crystals are ordered structures of charged microspheres trapped in the sheath of an rf discharge plasma. Using a monolayer crystal with a hexagonal lattice, Mach cones were excited by the radiation pressure of a focused laser beam. The beam was swept at a supersonic speed through the crystal, in a controlled and repeatable manner. A multiple Mach cone structure was observed, with at least three distinct Mach cones. The Mach angle relation was verified over a wide range of Mach numbers, for both the first and second cones. The sound speed, measured from the first Mach angle, was found to increase with the particle number density. Two methods of determining the particle charge and screening distance are developed, making use of the sound speed and an assumption of a Yukawa interparticle potential. Molecular-dynamics simulations of the experiment were carried out, using a monolayer of particles interacting through a Yukawa potential, and these show close agreement with the experiment.
本文介绍了等离子体晶体中马赫锥形成和结构的实验研究。等离子体晶体是被困在射频放电等离子体鞘层中的带电微球的有序结构。使用具有六边形晶格的单层晶体，通过聚焦激光束的辐射压力激发马赫锥。光束以超音速速度以可控且可重复的方式扫过晶体。观察到多重马赫锥结构，至少有三个不同的马赫锥。对于第一和第二锥，在很宽的马赫数范围内验证了马赫角关系。从第一马赫角测量的声速随粒子数密度增加。利用声速和对 Yukawa 粒子间势的假设，开发了两种确定粒子电荷和屏蔽距离的方法。使用通过 Yukawa 势相互作用的单层粒子进行了该实验的分子动力学模拟，结果与实验显示出密切的一致性。
