Dusty Plasma Experiments

Physics Objectives:

There are several physics objectives to the dusty plasma project. Among them are:

1. Understanding the 2-D (and eventually 3-D) transport of dust particles within a dust cloud with the ultimate objective of extending the present models of dust particle transport.
2. Understanding the formation and confinement of dust clouds in dc glow discharge plasmas.
3. Understanding the role of nonlinear effects on dust-driven plasma instabilities.
4. Understanding the thermodynamics properties of dusty plasmas.
5. Understanding the mechanisms for dust grain charging.

Experiments:

Dusty plasma experiments are conducted within the Basic Plasma Sciences Laboratory (PSL). At the center of our experimental effort is the use of the Particle Image Velocimetry (PIV) technique - which is used for making direct 2-D measurements of dust particle transport.

During Summer, 2003, a Stereoscopic Particle Image Velocimetry (stereo-PIV or 3D-PIV) system was installed in the Plasma Sciences Laboratory.

Experiments	Layout	Measurements
3-DPX Experiment		3D transport in dusty plasmas Thermodynamic properties of microparticle component of the plasma.
Dusty Plasma Experiment		2D & 3D particle transport in dusty plasmas Nonlinear effects on dust acoustic waves
Ring Experiment		Laboratory simulation of a planetary ring system Driven instabilities in a ring plane.

3DPX device:

• The 3DPX device is the laboratories newest experiment. It is specifically optimized to take advantage of the stereoscopic (3D) PIV system.
• Device assembly was completed in early 2003.
• The stereoPIV system was installed on DPX during Summer, 2003.
• Experiments now regularly make use of the stereoPIV diagnostic tool to make detailed measurements of three-dimensional particle flows in the device.
• Studies on 3DPX will focus on particle transport near the dust cloud - plasma boundary and investigations of the thermodynamic properties of the dust component of the plasma.

DPX device:

• In Summer, 2004, the DPX device underwent a major upgrade. The PIV computers, camera systems, synchronizer, and other major hardware components were updated.
• The DPX (Dusty Plasma Experiment) is the first plasma source that was used by the PSL to study dusty plasmas.
• The PSL's first investigations of particle transport in dusty plasmas using Particle Image Velocimetry (2D-PIV) were performed using DPX.
• Initial studies on DPX have focused on characterizing the confinement and 2-D and 3-D transport phenomena in dc glow discharge dusty plasmas.
• More recent studies have focused on high speed dust particle streams and dust acoustic waves in dusty plasmas.
• Experiments in the DPX device focus on studies of dust particle transport. In these experiments, both 3 micron Al₂O₃ (alumina) and 3 micron and 40 micron SiO₂ (silica) particles have been used as dust particles.
• The dust particles are placed on a small rectangluar tray and inserted into the plasma 1 to 4 cm below the anode. DC glow discharge argon plasmas are produced in the DPX device using both a biased anode (V_a ~ 200 - 250 V) and a biased cathode (V_c~ 0 to - 100 V) at pressures ranging from 90 to 250 mTorr.
• The physical arrangement of the electrodes and the dust cloud are shown HERE.

Ring Experiment:

• UPDATE:
  • The Ring Experiment required a major redesign due to leakage in the old vacuum vessel. The device has been rebuilt using a stainless steel 5-way cross and is now operational.
  • In addition to using this chamber for ring simulation pressures (p ³ 400 mTorr), it may be possible to force the particles to achieve a crystal-like state.
  • At lower pressures, large scale vortices are observed in the Ring Experiment dust clouds.
  • Follow THIS link for photographs of the rebuilt Ring Simulation Experiment.
    
    
• The initial interest in dusty plasmas began in the space environment where the charged dust is responsible for phenomena ranging from comet tails to planetary rings to nebula. In fact, interest in astrophysical dusty plasmas was initiated by the effort to explain the radial "spoke" structures observed in the Saturn ring system.
• Because there have only been a few in-situ measurements of the plasma and dust conditions near the outer planets, there is a very limited amount of detailed data on dust particle dynamics in the space environment.
• In this study, a planetary ring system will be simulated in a laboratory dusty plasma experiment and will be used to characterize the effects of applied perturbation to ring structures.