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Dusty Plasmas in the

Laboratory and Space

Bob Merlino

April 2003 APS Meeting Philadelphia, PA

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Outline

1) Introductionwhat 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

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plasma = electrons + ions Plasma

+

-

+

+

+

+

+

+

+

--

-

-

--

-

+

-

What is a dusty

plasma?

D

Debye

shielding

small particle

of solid matter

becomes

negativelycharged

absorbselectrons and

ions

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Dusty Plasma in the Universe

Dust represents much of the

solid matter in the universeand this component oftencoexists with the ionized

matter forming a dustyplasma.

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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

Solar nebula

planetary rings

interstellar medium

comet tails

noctilucent clouds

lightning

Microelectronic

processing

rocket exhaust

fusion devices

Natural Man-made

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Our solar systemaccumulated out

of a dense cloud of

gas and dust, formingeverything 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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An early temperature measurement in a dusty plasma.

A flame is a very weakly ionized plasma

that contains soot particles.

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Comet Hale-Bopp

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Spokes in Saturns B Ring

Voyager 2

Nov. 1980

Cassini-

HuygensJuly 2004

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Semiconductor Processing System

dust

silane (SiH4) + Ar + O2 SiO2 particles

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Semiconductor Manufacturing

dustSi

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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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electron

repulsion

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.

a

2

2

1

exp

akT

eV

m

kTenI

a

kT

eV

m

kTenI

i

S

i

iii

e

S

e

eee

Q = (4eoa) 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

0

0.5

1

1.5

2

0 20 40 60 80 100 120

Diameter (micron)2

0

0.5

1

1.5

0 20 40 60 80 100 120 140 160

Electron Energy (eV)

Glass

Graphite

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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PUMP

ANODEDISK

FIREROD

ROTATING DUSTDISPENSER

PLASMA COLUMN

HOT PLATE

B

VIDEOCAMERA

CONFINEDDUST GRAINS

GAS IN

GAS IN

Equipotential profiles

of an anode doublelayer

anode

Device for studying

the trapping of dust

in a dc glowdischarge

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DUST IN A GLOW DISCHARGE

N2

Vacuum

vessel

PS

+

BAnode

Dust Tray

Anode Glow

Plasma

Dust: kaolin (aluminum silicate)

E

mg

QE

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wavefronts

Dust Acoustic Wave Image

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dust mass

DA Dispersion relation

Monochromatic plane wave solutions

for Te = Ti = T

1

1d

dDA Z

m

kTCf

where = ndo/n+o

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Dust Acoustic Wave

Dispersion Relation

theory

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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 travelthrough 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 thebehavior of dusty plasmas in the laboratory

-charging mechanisms, waves

Technological applications of dusty plasmas arenow 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 dustyplasmas has yet to be studied in the lab

R = Mv/QB >> typical lab plasmas

Dusty plasmas may form strongly coupled

systems known as Coulomb Crystalsa new

area for plasma physics research

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Dusty Plasma

DUST

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RF Dusty Plasma Device