Particle Charge Determination in a Magnetized Dusty Plasma Flow

Abstract

Dusty plasmas consist of components typically found in a plasma (electrons, ions and neutral particles) as well as micrometer sized dust particles. The structural and dynamic properties of a dusty plasma system are governed by the dust particle charging state and the interaction of these particles with each other as well as the surrounding plasma and as a result of this, the knowledge of the exact charging state of the dust particles is very important. Theories such as Orbital Motion Limited (OML) and Allen-Boyd-Reynolds (ABR) theories as well as modified versions of these have been used to theoretically determine dust charge value in the past. Some recent experiments to determine particle charge indicate differences from theoretical models. This is particularly the case in the presence of a magnetic field. A molecular dynamic simulation has been created to study dust particle dynamics in the presence of a magnetic field. In a flowing system, a dust particle density gradient can build up due to the Lorentz force (similarly to the classical Hall effect). This dissertation will show multiple theories which have been developed to utilize this gradient to determine the particle charge in different coupling regimes. This is a new method for determining dust charge value which will be useful in many future experiments. Due to the interactive properties of dust particles, coupling of dust particles becomes an important factor. The coulomb coupling parameter Γ is defined as a ratio of interactive potential energy to thermal kinetic energy. With this coupling parameter, regimes of liquid, solid and gas-like can be defined. Using a similar experimental system to that of a classical Hall effect, separate theories for calculation of dust charge were developed for the low coupling (”gas-like”) and high coupling (”solid-like”/crystalline) regimes. These two new methods will help increase the accuracy of dust charge determination in future dusty plasma research.