Jimmy Schmoke

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.

A New Inductively Driven Plasma Generator (IPG6)—Setup and Initial Experiments

As part of the partnership between the Center for Astrophysics, Space Physics and Engineering Research (CASPER) at Baylor University and the Institute of Space Systems (IRS) at the University of Stuttgart, a new design for a modular inductively driven plasma generator (IPG) is being developed and tested within CASPER and the IRS. The current IPG design is built on a well-established heritage of modular IPGs designed and operated at IRS. This latest IPG source enables the electrodeless generation of high-enthalpy plasmas and will provide CASPER researchers with the ability to operate with various gases at plasma powers of approximately 15 kW. It will also provide minimized field losses and operation over a wide scope of parameters not possible using existing designs requiring flow-controlled stabilization.

The effect of electrode heating on the discharge parameters in complex plasma experiments

Thermophoresis is a tool often applied in complex plasma experiments. One of the usual stated benefits over other experimental tools is that electrode temperature changes required to induce thermophoresis do not directly influence the plasma parameters. From electronic data, plasma emission profiles in the sheath, and Langmuir probe data in the plasma bulk, we conclude that this assumption does not hold. An important effect on the levitation of dust particles in argon plasma is observed as well. The reason behind the changes in plasma parameters seems to be the change in neutral atom density accompanying the increased gas temperature while running at constant pressure.

Investigation of dust wake field oscillations

Wakefield oscillations created by the ion wakefield existing below a dust particle within the plasma sheath generated above a powered lower electrode in a GEC rf reference cell carry information about the plasma sheath, the dust particle charge and the speed of the streaming ions. An experimental method to investigate such wakefield oscillations is discussed.

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.