Self-confinement of finite dust clusters in isotropic plasmas

Abstract

Finite two-dimensional dust clusters are systems of a small number of charged grains. The self-confinement of dust clusters in isotropic plasmas is studied using the particle-in-cell method. The energetically favorable configurations of grains in plasma are found that are due to the kinetic effects of plasma ions and electrons. The self-confinement phenomenon is attributed to the change in the plasma composition within a dust cluster resulting in grain attraction mediated by plasma ions. This is a self-consistent state of a dust cluster in which grain's repulsion is compensated by the reduced charge and floating potential on grains, overlapped ion clouds, and depleted electrons within a cluster. The common potential well is formed trapping dust clusters in the confined state. These results provide both valuable insights and a different perspective to the classical view on the formation of boundary-free dust clusters in isotropic plasmas.

Plasma flow around and charge distribution of a dust cluster in a rf discharge

“…In twoparticle chains it has been found numerically that the negative charge of the downstream grain is reduced because the ion focus of the upstream grain increases the ion current onto the grain 19,20 . Miloshevsky et al 21,22 investigated the charging of a rigid two-dimensional hexagonal dust cluster consisting of 19 dust grains and its impact on the plasma environment with a 2d PIC/MD simulation. In absence of a streaming plasma (isotropic case) an energetically favorable configuration of the dust cluster was found for an inter-particle distance between dust grains of ∼ 0.6λ De due to the creation of a potential well by overlapping ion clouds around each dust grain.…”

A treecode to simulate dust–plasma interactions

“…The shape and size of dust is also variable, as they can grow through aggregation [4] or shrink through evaporation and violent processes such as electrostatic breakup [5]. The co-dependence of these processes, and many others, in a dusty plasma has led to their alternative name of "complex plasmas", and is manifest in surprising phenomena such as the self-organization of dust grains into crystal-like structures [6]. Although some approximate analytic theories exist to describe fundamental processes in a dusty plasma, the inherent complexity of these systems necessitates computer simulations to resolve their full detail.…”

Formation of droplets in weightless complex plasmas

“…[1][2][3] Understanding their formation and the mechanisms controlling their behaviour is important for the development of, for example, nanomaterials. [4] Under the influence of an external confinement, the formation of microparticle (dust) clusters or Yukawa balls consisting from only a few up to thousands of dust particles has been observed. [5] In these systems, the microparticles attain high negative charges due to the fluxes of plasma ions and electrons onto their surfaces.…”

“…[10][11][12] The formation of these clusters was predicted to take place for dense microparticle clouds due to the mutual shadowing of plasma flows onto these particles, [13][14][15][16] or due to the fact that newly created ions in the space between microparticles will lead to an effective positive space charge with overlapped ion clouds as well as reduced microparticle charge and electron number density in these dense clouds. [4,17] A self-confinement of pairs of microparticles can also occur due to the non-reciprocity of the inter-particle interaction. [18] Another mechanism that could cause an effective attraction between the negatively charged microparticles is the ion drag force, which is the force induced by ions streaming past the microparticles.…”