Jerry Reay

Dusty plasma correlation function experiment

Abstract Dust particles immersed within a plasma environment, such as those in protostellar clouds, planetary rings or cometary environments, will acquire an electric charge. If the ratio of the inter-particle potential energy to the average kinetic energy is high enough the particles will form either a “liquid” structure with short-range ordering or a crystalline structure with long range ordering. Many experiments have been conducted over the past several years on such colloidal plasmas to discover the nature of the crystals formed, but more work is needed to fully understand these complex colloidal systems. Most previous experiments have employed monodisperse spheres to form Coulomb crystals. However, in nature (as well as in most plasma processing environments) the distribution of particle sizes is more randomized and disperse. This paper reports experiments which were carried out in a GEC radio frequency reference cell modified for use as a dusty plasma system, using varying sizes of particles to determine the manner in which the correlation function depends upon the overall dust grain size distribution. (The correlation function determines the overall crystalline structure of the lattice.) Two-dimensional plasma crystals were formed of assorted glass spheres with specific size distributions in an argon plasma. Using various optical techniques, the pair correlation function was determined and compared to those calculated numerically.

Phase transitions in a non-monodisperse dusty plasma

Summary form only given. In semiconductor manufacturing, contamination due to particulates significantly decreases the yield and quality of device fabrication, therefore increasing the cost of production. Dust particle clouds can be found in almost all plasma processing environments including both plasma etching devices and plasma deposition processes. Many experiments have been conducted over the past decade on such colloidal plasmas in an attempt to discover the character of the systems formed, but additional work is needed in order to fully understand the physics behind these structures. The majority of complex plasma experiments to date have employed monodisperse spheres when forming ordered dusty plasma systems. However, in the majority of plasma processing environments the particle size distributions are obviously more randomized and disperse. This paper reports experiments carried out in a GEC rf reference cell modified for use as a complex plasma system. Non-monodisperse particles were used to determine the manner in which phase transitions and other thermodynamic properties depend upon the overall dust grain size distribution. Two dimensional (2D) plasma crystals were formed in an Argon plasma using assorted glass spheres with specific size distributions. Employing various, standard optical techniques, the pair correlation function was then determined for different pressures and powers and compared to measurements obtained for monodisperse spheres.