Dusty Plasmas in the Laboratory and Space

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Dusty Plasmas in the Laboratory and Space
April 2003 APS Meeting Philadelphia, PA

• Bob Merlino

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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

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What is a dusty plasma?
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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.

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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

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DUSTY PLASMAS
Natural
Man-made

• Solar nebula
• planetary rings
• interstellar medium
• comet tails
• noctilucent clouds
• lightning

• Microelectronic processing
• rocket exhaust
• fusion devices

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

Rosette Nebula
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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

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A flame is a very weakly ionized plasma that
contains soot particles.
An early temperature measurement in a dusty
plasma.
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Comet Hale-Bopp
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Spokes in Saturns B Ring

• Voyager 2
• Nov. 1980

Cassini- Huygens July 2004
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Semiconductor Processing System
silane (SiH4) Ar O2
? SiO2 particles
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Semiconductor Manufacturing
Si
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Physics Today August 1994
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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

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The Charge on a Dust Grain
In typical lab plasmas Isec Ipe 0
Electron thermal speed gtgt 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
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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
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Dust Charge Measurements
Walch, Horanyi, Robertson, Phys. Rev. Lett. 75,
838 (1995)
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Devices for producing dusty plasmas
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RF Dusty Plasma Devices
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Device for studyingthe trapping of dustin a dc
glow discharge
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DUST IN A GLOW DISCHARGE
Dust kaolin (aluminum silicate)
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Dust Acoustic Wave Image
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DA Dispersion relation
Monochromatic plane wave solutions for Te Ti
T
where d ndo/no
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Dust Acoustic WaveDispersion Relation
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Shocks in Dusty Plasma
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Shocks in Dusty Plasma- results
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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

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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

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• 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 gtgt typical lab plasmas
• Dusty plasmas may form strongly coupled systems
  known as Coulomb Crystals a new area for plasma
  physics research

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Dusty Plasma
DUST
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RF Dusty Plasma Device