Dynamic Phenomena in Complex Plasmas N.F. Cramer, S.V. Vladimirov, A.A. Samarian and B.W. James

1. The University of Sydney Dynamic Phenomena in Complex Plasmas N.F. Cramer, S.V. Vladimirov, A.A. Samarian and B.W. James School of Physics, University of Sydney, Australia

2. Dusty Plasmas at the University of Sydney • N. Cramer, S. Vladimirov, S. Maiorov (Theoretical Physics): Theory of Laboratory and Astrophysical Dusty Plasmas • B. James, A. Samarian, F. Cheung, W. Tsang (Applied and Plasma Physics): Dusty Plasma Experiments • M. Wardle (Research Centre for Theoretical Astrophysics): Charged Dust in Interstellar Clouds • Collaborators: N. Prior, O. Vaulina, O. Ishihara, V. Tsytovich, F. Verheest, J. Sakai, M. Hellberg.

3. Dynamic Phenomena: Self-excited motions Oscillations Waves Vortex motions Rotation of Fine Dust Clusters in Axial Magnetic Field Dust Grains as Diagnostic Tool for Sheath Measurement in RF-Discharge Plasma Laser Excited Oscillations in Vertically Aligned Structures

4. Dynamics of Single Particle • Potential energy of a dust grain with variable (solid lines) and constant charge (dashed lines) in the plasma sheath

5. Charging dynamics of the macroparticle of mg=105mp with and without an ion flow. • The time step is =3.410-10s. • Total simulation time is t0=190 and  =6.5 x 10-8s. • The asymptotic charge is • (a) Z =842 in the absence of the ion flow, M2=0 • (b) Z=1067 for M2=0.6 and • (c) Z=1146 for M2=2.4

6. Contour plots of the ion density, for three values of the speed of the ion flow (one is subsonic with M2=0.6, and two supersonic, with M2=1.2 and M2=2.4). • A strong ion focus is formed at the distance of a fraction of the electron Debye length behind the dust grain

7. Dynamics of Few Particles • Instabilities of Dust Particle Arrangements (Presentation of S Vladimirov et al.) • Rotation of Dust Coulomb Clusters in Axial Magnetic Field (Presentation of Cheung et al.) • Laser Excited Oscillations in Vertically Aligned Structures (Poster of Prior et al.)

8. 02.9.00AD Laser Driven Oscillations of Few Particles Structures(Poster of Prior et al.)

9. 02.9.00AD Instability of a string of 3 particles(paper of Vladimirov)

10. 02.9.00AD Rotational motion

11. Dynamics of Many Interacting Particles • Various kinds of dust grain self-excited motion have been observed : • Vertical oscillations in mono-layer dust structure, • Complex wave motions in multi-layer structures, • Vortex motion caused by an introduction of an additional electrode, • Rotation and oscillation in non symmetrical electrode configurations.

12. Vibrational Modes of dust grain arrays • Vibrations in simple versions of lattices of dust grains embedded in the sheath region near a horizontal electrode. Understanding the modes provide useful diagnostics and aid in analysing critical phenomena and phase transitions in such systems • Horizontal vibrations of dust grains within one layer lead to acoustic-type modes. Vertical vibrations of dust grains in the layer lead to optical-mode-like dispersive waves (Vladimirov, Shevchenko, and Cramer, 1997-1998)

13. Vibrations of a one-dimensional horizontal chain of grains of equal masses M and constant charge Q

14. Vertical Oscillation 30 mTorr and 100 W 30 mTorr and 35 W 30 mTorr and 15 W • For a mono-layer structure, the dust particles begin to oscillate spontaneously in the vertical direction when the pressure is decreased below a critical value. • The amplitude of the oscillation is several millimetres and the frequency is greater than 10Hz. When the rf input power is decreased, the amplitude increases. • For pressures below 35mTorr, the amplitude increases dramatically. This increase is greater for lower rf powers.

15. Vertical Oscillation Carbon Particles (2.1±0.1m in diameter) 1 Amp (mm) P=20 W P=35 W 0,8 P=50 W 0,6 P=65 W 0,4 P=80 W P=100 W 0,2 P=120 W 0 10 15 20 25 30 35 40 Pressure(mTorr)

16. Second, consider two vertically ordered one-dimensional horizontal chains of grains with constant charges ion flow negatively charged electrode

17. The effect of the wake behind each grain in the Mach cone (Vladimirov and Nambu, 1995; Vladimirov and Ishihara 1996-1998) -----------> ion -----------> flow -----------> to the -----------> electrode -----------> e l e c t r o d e

18. Modes of vibrations • There are two modes of oscillations:

19. Modes of a chain of rod-like particles

20. Longitudinal compressive waves in 3-D structure (side) 1sec 2sec 3sec • We observed that density waves which travel downwards with a wavelength l=3mm and a period T=4x10-2s, were generated by decreasing the input power or pressure, and by increasing the number of dust particles in the structure dp= 6.13 mm, P= 60 W, p= 30 mTorr

21. Heartbeat Oscillation & Surface Waves Peaks 0 6 0 5 1sec 2sec 0.02sec 0.04sec 0.06sec 0.08sec Wavelength l=6mm Velocity v=1.5ms-1

22. Surface Waves 02.9.00AD Wavelength l=6mm Velocity v=1.5ms-1

23. 02.9.00AD Void surface waves

24. Rotational Motion 02.9.00AD

25. (Top view) Pin Electrode Illustration of Dust Vortex

26. Vortex Motion 02.9.00AD