Dusty Plasmas in the Laboratory and Space

1. April 2003 APS Meeting Philadelphia, PA Dusty Plasmas in the Laboratory and Space Bob Merlino

2. Outline • Introduction – what is a dusty plasma and where are they found • the charging of dust in a plasma • devices for producing dusty plasmas • waves in dusty plasmas

3. plasma = electrons + ions small particle of solid matter • absorbs electrons and ions • becomes negatively charged • Debye shielding What is a dusty plasma?

4. Dusty Plasma in the Universe Dust represents much of the solid matter in the universe and this component often coexists with the ionized matter forming a dusty plasma.

5. Importance of Charged Dust • the dust acquires an electrical charge and thus is subject to electromagnetic as well as gravitational forces • the charged dust particles participate in the collective plasma processes

6. Solar nebula planetary rings interstellar medium comet tails noctilucent clouds lightning Microelectronic processing rocket exhaust fusion devices DUSTY PLASMAS Natural Man-made

7. Our solar system accumulated out of a dense cloud of gas and dust, forming everything that is now part of our world. Rosette Nebula

8. Noctilucent Clouds (NLC) • Occur in the summer polar mesosphere (~ 82 km) • 50 nm ice crystals • Associated with unusual radar echoes and reductions in the local ionospheric density

9. A flame is a very weakly ionized plasma that contains soot particles. An early temperature measurement in a dusty plasma.

10. Comet Hale-Bopp

11. Spokes in Saturn’s B Ring • Voyager 2 • Nov. 1980 Cassini- Huygens July 2004

12. dust Semiconductor Processing System  SiO2 particles silane (SiH4) + Ar + O2

13. dust Semiconductor Manufacturing Si

14. Physics Today August 1994

15. Dust Charging Processes • electron and ion collection • secondary emission • UV induced photoelectron emission • Total current to a grain = 0 •  I = Ie + Ii + Isec + Ipe = 0

16. electron repulsion a ion enhancement The Charge on a Dust Grain In typical lab plasmas Isec = Ipe = 0 Electron thermal speed >> ion thermal speed so the grains charge to a negative potential VS relative to the plasma, until the condition Ie = Ii is achieved. Q = (4peoa) VS

17. Typical Lab Plasma For T e = Ti = T in a hydrogen plasma VS =  2.5 (kT/e) If T  1 eV and a = 1 m, Q   2000 e Mass m  5  1012 mp

18. 2 1.5 Graphite 1 Glass 0.5 0 0 20 40 60 80 100 120 140 160 Electron Energy (eV) Dust Charge Measurements Walch, Horanyi, & Robertson, Phys. Rev. Lett. 75, 838 (1995)

19. Devices for producing dusty plasmas

20. RF Dusty Plasma Devices

21. Equipotential profiles of an anode double layer anode Device for studyingthe trapping of dustin a dc glow discharge

22. B QE N2 Anode Anode Glow Plasma E Dust Tray + mg PS Vacuum vessel DUST IN A GLOW DISCHARGE Dust: kaolin (aluminum silicate)

23. wavefronts Dust Acoustic Wave Image

24. dust mass DA Dispersion relation Monochromatic plane wave solutions for Te = Ti = T where d = ndo/n+o

25. theory Dust Acoustic WaveDispersion Relation

26. Shocks in Dusty Plasma

27. Shocks in Dusty Plasma- results

28. Shocks in dusty plasmas Conclusions • Ion acoustic compress-ional pulses are observed to steepen as they travel through a dusty plasma • Relevant to astrophysical contexts where density disturbances travel through dust clouds

29. Conclusions and Outlook • Only recently have we begun to explore the behavior of dusty plasmas in the laboratory -charging mechanisms, waves • Technological applications of dusty plasmas are now being exploited -ceramic deposition – composites -growth of nanosize particles -diamond growth and deposition on metals

30. Dusty plasmas in space are usually embedded in magnetic fields. This aspect of dusty plasmas has yet to be studied in the lab R = Mv/QB >> typical lab plasmas • Dusty plasmas may form strongly coupled systems known as Coulomb Crystals – a new area for plasma physics research

31. Dusty Plasma DUST

32. RF Dusty Plasma Device