Search

A description is given of the Magnetized Dusty Plasma Experiment (MDPX) at Auburn University that was designed to study the physics of highly magnetized low temperature plasmas and magnetized dusty plasmas. The central components of the MDPX are a superconducting solenoid capable of operation at magnetic fields up to 4 T, and a parallel plate RF discharge plasma. Results from some of the initial experiments will be presented.A description is given of the Magnetized Dusty Plasma Experiment (MDPX) at Auburn University that was designed to study the physics of highly magnetized low temperature plasmas and magnetized dusty plasmas. The central components of the MDPX are a superconducting solenoid capable of operation at magnetic fields up to 4 T, and a parallel plate RF discharge plasma. Results from some of the initial experiments will be presented.

Melting of a monolayer plasma crystal was induced by an electric pulse. We investigated, how structural parameters like defect fraction and correlation lengths as well as dynamical properties like the particle kinetic energy changed during the recrystallisation. As an indication of the phase transition, the change of the Lindemann parameter and the Coulomb coupling parameter were considered.

Complex plasmas are an ideal model system to investigate laminar fluids as they allow to study fluids at the kinetic level. At this level we are able to identify streamlines particle by particle. This gives us the ability to research the behaviour of these streamlines as well as the behaviour of each individual particle of the streamline.We carried out our experiments in a modified GEC‐RF‐Reference cell. We trapped the particles within two glass rings and forced them to form a circular flow by using several stripe electrodes. In this flow the particles behave like an ideal fluid and form streamlines. By putting an obstacle into the flow we reduce the cross‐section. To pass through this constricted cross‐section some streamlines have to reconnect. After the obstacle the streamlines split up again. An analysis how streamlines split up and reconnect as result of external pressure on the fluid in our system is presented here.Streamlines also occur if two clouds of particles penetrate each other. We call this ...

To complete our picture of general complex plasmas, experiments under the influence of high magnetic fields have been carried out in a radio frequency (rf) discharge with and without embedded micro‐particles. The influence of the strong magnetic field on the plasma with respect to its homogeneity as well as on the isotropy of the particle interaction was studied. We observed a filamentation of the plasma at low pressures and low powers even in the absence of particles. The plasma filaments moved around — traced by embedded particles — and suddenly changed to a crystalline like arrangement.

The plasma parameters of a complex plasma have been measured under microgravity conditions using a cylindrical Langmuir probe. One‐ and two‐dimensional profiles of dusty and void regions are obtained, which show a flattened distribution of plasma potential and electron density. Characteristic changes of the plasma parameters correlate with the geometry of the particle cloud.

If we assume that the interaction potential of a dust particle in a plasma is of a Yukawa type, then we can determine the particle charge and the screening length from its trajectory during central collisions. We present a theoretical approach taking into account, that the particles are horizontally confined and that friction may influence the trajectories. In addition we show former results (1) based on this theory in the limit of negligible friction and confinement forces.

General properties of strongly coupled colloidal plasmas are briefly summarised, and their properties of being able to “condense” into a self-organised liquid and crystalline form is discussed. Both laboratory and microgravity aspects of the research into this new form of matter are described and the theoretical constraints are compared with available measurements. Finally, the phase transition solid-liquid-gaseous is investigated using measurements of the “normalised interaction cross section,” ∑σp, derived from “molecular diffusion of the colloid component.