Your Federal Quarterly Tax Payments are due April 15th Get Help Now >>

Dusty Plasmas in the Laboratory and Space by shuifanglj

VIEWS: 8 PAGES: 32

									April 2003 APS Meeting Philadelphia, PA



Dusty Plasmas in the
Laboratory and Space

           Bob Merlino
                Outline
1) Introduction – what is a dusty plasma and
   where are they found
2) the charging of dust in a plasma
3) devices for producing dusty plasmas
4) waves in dusty plasmas
     What is a dusty
       plasma?
plasma = electrons + ions

 small particle
 of solid matter
  • absorbs
    electrons and
    ions

  • becomes
    negatively
    charged

  • Debye
    shielding
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.
 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
          DUSTY PLASMAS
        Natural               Man-made

•   Solar nebula          • Microelectronic
•   planetary rings         processing
•   interstellar medium   • rocket exhaust
•   comet tails           • fusion devices
•   noctilucent clouds
•   lightning
                 Our solar system
                 accumulated out
                 of a dense cloud of
                 gas and dust, forming
                 everything that is now
                 part of our world.

Rosette Nebula
  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
A flame is a very weakly ionized plasma
      that contains soot particles.




An early temperature measurement in a dusty plasma.
Comet Hale-Bopp
Spokes in Saturn’s B Ring

                     Voyager 2
                     Nov. 1980




                     Cassini-
                     Huygens
                     July 2004
  Semiconductor Processing System

    dust




silane (SiH4) + Ar + O2  SiO2 particles
     Semiconductor Manufacturing




Si                      dust
Physics Today
August 1994
         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
    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.
                                        electron
                                        repulsion
                                                       a

                                              Q = (4peoa) VS

                                    ion enhancement
    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
           Dust Charge Measurements

Walch, Horanyi, & Robertson,
Phys. Rev. Lett. 75, 838 (1995)




                                    2


                                  1.5
                                                                         Graphite

                                   1


                                  0.5                  Glass


                                   0
                                        0   20   40   60   80    100     120   140   160
                                                  Electron Energy (eV)
Devices for producing
   dusty plasmas
RF Dusty Plasma Devices
Device for studying
the trapping of dust
    in a dc glow
      discharge




                          Equipotential profiles
                          of an anode double
                          layer
                       anode
          DUST IN A GLOW DISCHARGE


QE                        B                    N2
                                       Anode
        Anode Glow
          Plasma
                              E

        Dust Tray                               +
mg
                                               PS
     Vacuum
      vessel
          Dust: kaolin (aluminum silicate)
Dust Acoustic Wave Image

      wavefronts
   DA Dispersion relation
Monochromatic plane wave solutions
         for Te = Ti = T




where d = ndo/n+o         dust mass
Dust Acoustic Wave
Dispersion Relation




        theory
Shocks in Dusty Plasma
Shocks in Dusty Plasma- results
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
       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
• 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
Dusty Plasma




               DUST
RF Dusty Plasma Device

								
To top