Rotation of Coulomb crystals in a magnetized inductively coupled complex plasma

Under suitable conditions, micron-sized dust particles introduced into inductively coupled argon plasma form a stable microscopic crystal lattice, known as a Coulomb (or plasma) crystal. In the experiment described, an external axial magnetic field was applied to various configurations of Coulomb crystal, including small crystal lattices consisting of one to several particles, and large crystal lattices with many hundreds of particles. The crystals were observed to rotate collectively under the influence of the magnetic field. This paper describes the experimental procedures and the preliminary results of this investigation

Critical roles of arginine in growth and biofilm development by Streptococcus gordonii

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112199/1/mmi13023.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112199/2/mmi13023-sup-0001-si.pd

Particles as probes for complex plasmas in front of biased surfaces

An interesting aspect in the research of complex (dusty) plasmas is the experimental study of the interaction of micro-particles with the surrounding plasma for diagnostic purposes. Local electric fields can be determined from the behaviour of particles in the plasma, e.g. particles may serve as electrostatic probes. Since in many cases of applications in plasma technology it is of great interest to describe the electric field conditions in front of floating or biased surfaces, the confinement and behaviour of test particles is studied in front of floating walls inserted into a plasma as well as in front of additionally biased surfaces. For the latter case, the behaviour of particles in front of an adaptive electrode, which allows for an efficient confinement and manipulation of the grains, has been experimentally studied in dependence on the discharge parameters and on different bias conditions of the electrode. The effect of the partially biased surface (dc, rf) on the charged micro-particles has been investigated by particle falling experiments. In addition to the experiments we also investigate the particle behaviour numerically by molecular dynamics, in combination with a fluid and particle-in-cell description of the plasma.Comment: 39 pages, 16 figures, submitted to New J. Phy

Mode-spectral analysis of 2D Coulomb clusters with fluctuating charges

The mode spectra of small $N = 3, 7, 12$ clusters of dust particles with fluctuating charges are analyzed. Particular attention is paid to the influence of correlated and uncorrelated charge fluctuations on the oscillation mode spectra of these clusters. It is found that the main signature of the correlated charge fluctuations is the shift of the lowest-frequency (shear) mode; other modes are split/shifted according to their mode number and the weight of the shear and compressional parts in their oscillation pattern. This is useful for diagnostics as the character of dust charge fluctuations extracted from the analysis of the cluster mode spectra provides important information on the plasma correlation length

Physics and applications of complex plasmas

At the frontiers of physics and chemistry lies the new and rapidly emerging area of complex plasma systems. The study of complex plasma systems that contain colloid nano/microscopic particles is now actively pursued in a diverse range of scientific fields — from plasma and gas discharge physics, to astrophysics, materials science and engineering. This book highlights, in a systematic, insightful, and perceptive way, the fundamental physics and industrial applications of complex plasmas, with emphasis on the conditions relevant to laboratory gas discharges and industrial plasma reactors. It provides a specialized and comprehensive description of the most recent theoretical, experimental, and modeling efforts to understand the unique properties of complex plasma systems involving the stability, dynamics, and self-organization of colloid particles and their associations. Special attention is focused on the physical understanding of up-to-date developments in major technological applications of micron and nano-sized particles. Each chapter is presented in a concise and comprehensive manner, with a categorized overview of the underlying physics followed by an in-depth description. The book will appeal to scientists and researchers as well as undergraduate and graduate students wishing to explore the flourishing interdisciplinary field of complex plasma systems.</p

Charge on the dust in the plasma

The grain in the plasma gets charged until the net plasma flux to the grain surface vanishes. In the absence of any analytical formula, this ambipolar condition is utilized to compute the grain charge indirectly. The present work proposes an approximate analytical expression for the grain charge that is exact in the asymptotic limit and in which the relative error between analytical and numerically computed solutions is less than 3%. Using this formula, we show that, much like the plasma sheath, the Bohm criterion is satisfied near the dust surface.5 page(s

Shear instability in magnetized, collisional dusty plasmas

The shear instability of magnetized, collisional dusty plasma is investigated in the present work. It is demonstrated that the relative drift between the charged dust and magnetised electrons and ions which give rise to the Hall effect is crucial to this instability. Although the nature of present shear instability is similar to the Kelvin-Helmholtz instability, the role of magnetic field in the present case is important in destabilising waves. The maximum growth rate of the instability is proportional only to the shear gradient and is independent of the ambient magnetic field strength. Most unstable wavenumber is a function of ambient dust parameters.5 page(s