"Thesis Completion"

After 1 year of hardwork, I have finally finished my 200+ pages thesis titled "Dust clusters in magnetized plasma". There are many people who have supported me in this thesis who I must acknowledge, but more on that later. If you would like to share my happiness in this event, please leave a message here (require hotmail or msn account to sign in).

This is the abstract of my thesis:

"This thesis is the first detailed experimental investigations of dust clusters in magnetized rf discharge plasma. Our experiments performed in a weakly magnetized (up to 100 G) inductive rf discharge show that dust cluster rotation is dependent on the number of particles and the magnetic field. Comparson of our experimental results with current theoretical models demonstrated that dust rotation is largely due to momentum impact transferred from the partially magnetized ions in the plasma to the dust particles.

Particles in dust clusters were found to fluctuate predominantly in the azimuthal direction rather than in the radial direction. A strong correlation between the packing sequence probability of a cluster and the particle fluctuation was observed. A magnetic field has been shown to decrease the amount of particle fluctuations in a dust cluster.

In our experiments, it was found that the radial positions of the dust particles self-adjusted to accommodate for the change in the ambipolar electric field. It was also found that dust particles can be confined by a magnetically-induced electrostatic trap.

Furthermore, our experimental results demonstrated the possibility in manipulating dust particles with 3 degrees of freedom using a magnetic field as an external, controlled parameter. The implications of dust rotation due to a magnetic field in industrial applications, such as the removal of dust contamination in the manufacture of microelectronics and the fabrication of micro- and nano- devices in nanotechnology, are discussed."

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Here is the "Table of Contents":

1. Introduction

1.1. Dusty plasma

1.1.1. What is dusty plasma?
1.1.2. Examples of dusty plasma
1.1.3. Classification of dust plasma
1.1.4. Dusty plasma research

1.2. Dust dynamics and transport

1.2.1. Innovations from dust dynamics and transport
1.2.2. Dust dynamics in magnetic field

1.3. Current theoretical models on dust rotation

1.3.1. Konopka’s model
1.3.2. The choice of Coulomb logarithm in ion drag force estimation
1.3.3. Ishihara’s model
1.3.4. Kaw’s model
1.3.5. Shukla's model

1.4. Aim, outlines, and outcomes of this thesis

2. The experimental apparatus

2.1. The plasma chamber
2.2. The dust particles and the shaker
2.3. The making of dust clusters and crystals
2.4. The magnetic coil
2.5. The particle imaging and tracking system

3. Structures of dust clusters and crystals

3.1. Planar dust clusters in experiments

3.1.1. Summary of experimental conditions
3.1.2. L-Planar and S-Planar clusters
3.1.3. Cluster radius and radial distance
3.1.4. Metastable states

3.2. Planar dust clusters in computer simulations

3.2.1. Cluster eccentricity and inter-ring twist
3.2.2. Cluster energy
3.2.3. Our models for computer simulations
3.2.4. Packing sequences
3.2.5. Inter-ring twist spectrum
3.2.6. Energy and inter-ring twist relation
3.2.7. Influence of cluster eccentricity on inter-ring twist and energy

3.3. Other types of dust clustes and crystals

3.3.1. Summary of experimental conditions
3.3.2. Particles strings and three-dimensional clusters
3.3.3. Large crystals and annular crystals

3.4. Magnetically induced confinement of dust particles

3.4.1. Confinement electric field
3.4.2. The effect of axial magnetic field on confinement electric field
3.4.3. Intermediate clusters and magnetic confinement of dust particles
3.4.4. Superposition of electrostatic potentials and translational force

3.5. Summary

4. Rotation of dust clusters and crystals

4.1. Planar cluster rotation

4.1.1. Properties of the planar cluster rotation
4.1.2. Angular velocity
4.1.3. Angular velocity saturation
4.1.4. Angular momentum
4.1.5. Threshold magnetic field
4.1.6. Phase diagram and periodic pause
4.1.7. Translational force
4.1.8. Cylindrical assymmetry in confinement potential

4.2. Rotation of other types of dust clusters and crystals

4.2.1. Rotation of intermediate clusters
4.2.2. Rotation of particle strings and three dimensional clusters
4.2.3. Rotation of large crystals and annular crystals

4.3. Comparison of experimental results with current theroies

4.3.1. With reference to konopka's model
4.3.2. With reference to Ishihara's model
4.3.3. With reference to Kaw's model
4.3.4. With reference to Shukla's model

4.4. Further remarks on dust rotation

4.4.1. Neutral gas flow
4.4.2. Dust charge gradient
4.4.3. Divergence of magnetic field

4.5. Summary

5. Fluctuations of planar dust clusters

5.1. Cluster instabilities

5.1.1. Radial instability
5.1.2. Azimuthal instability
5.1.3. Total instability and instability ratio

5.2. Cluster instabilities versus number of particles

5.2.1. Radial instabilites versus number of particles
5.2.2. Azimuthal instability coefficient versus number of particles
5.2.3. Dominance of azimuthal component in cluster instability
5.2.4. Total instability coeffiecient versus number of particles

5.3. Cluster instabilites and magnetic field

5.3.1. Radial and azimuthal instabilities versus magnetic field
5.3.2. Total instability coefficient versus magnetic field

5.4. Further remarks on dust fluctuations

5.5. Summary

6. Future applications

6.1. Dust removal
6.2. Plasma diagnostics
6.3. Magnetic manipulation device
6.4. Thin film coating with magnetron sputtering
6.5. Particle assisted ion etching

7. Conclusion

8. Appendix

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This is some of the behind the scene photos of the thesis construction process over the last few days.

We used HP premium choice laser paper for the thesis. They are the highest quality acid-free, uncoated paper with maximum smoothness and brightness for the high quality graphics in the thesis.

Here is a test we did on the comparison of the quality of the paper.

Printing thesis on our color laserjet.

After binding, this is my 200+ pages thesis.

And the graphics are just superb.

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Lastly, I am deeply grateful to a group of people without which the completion of this thesis would not be possible. In particular, I would like to highlight three very important people. Firstly, I would like to thank my co-supervisor, Dr. Alex Samarian, for the vast amount of knowledge he taught me not only in Physics, but also in life. His innovative ideas led the project into a new direction. More importantly, his encouragement to express my visualization skills and artistic ideas during my scientific research had resulted in many illustrations and concepts seen throughout this thesis. Secondly, I would like to thank my former colleague, Dr. Nathan Prior, for his help in building my experimental apparatus and the mechanical skills he passed onto me. His unconditional contribution is a key element in the success of this project. Thirdly, I would like to thank my supervisor, Prof. Brian James, for his leadership in this project and his help in my transfer of PhD to the University of Sydney. His comments and suggestions are part of what constructed the final form of this thesis.

Thanks must go to three talented students: Cameron Ford and Stephen Barkby with their help in developing the computer routines in the simulation of planar cluster systems; and Christopher Brunner for his help in the analysis of cluster instabilities.

Thanks must go to the University of Sydney. This includes Dr. Nicole Bordes and the Sydney Regional Scientific Visualization Laboratory for their help in scientific visualization.

Thanks must go to the Flinders University of South Australia. This includes my former supervisor, Dr. Leon Mitchell, for his introduction into the field of dusty plasma; the technicians from the electrical and mechanical workshop, Bob Northeast, Mike Mellow, Peter Mariner at the School of Physics for the construction of the experimental apparatus; Dr. Michelle Hale and the School of Biological Sciences for the use of the image acquisition system; and Ms. Katie Green and the School of Chemistry for the use of the copper vapor deposition unit.

Thanks must go to the Australian Research Council for their financial support of this project over the last three and a half years.

Thanks must go to the State Key Laboratory of Materials Modifications by Beams at the Dalian University of Technology. This includes Jayson Ke Jiang for contacting me through our research website and thus initiated our collaborative researches and Lu-Jing Hou for repeating his computer simulations specifically for my experimental conditions.

Lastly, I would like to thank my family for their unconditional support both financially and emotionally in the last 25 years. Without their faith in me, I could not have endured this one year of painstaking thesis writing. In particular, I am in great debts to my beloved mother and grandmother as I will never be able to compensate the number of fine lines that have appeared on their faces over this period of time.

Felix Cheung

31/03/2005