Transcript Coulomb Crystal Experiments in Dusty Plasmas

Coulomb Crystal Experiments
in Dusty Plasmas
J.Goree
Dept. of Physics and Astronomy, University of Iowa
supported by DOE, NASA, NSF
Students & Postdocs:
V. Nosenko, S. Nunomura, R. Quinn, S. Samsonov
Forces Acting on Particles
For a particle of radius rd:
Force rd
• Electric
Force rd2
• Coulomb collision drag (due to ion flow)
• Gas drag
• Radiation pressure from laser manipulation
Force rd3
• Gravity
Electrostatic trapping of particles
electrode
electrode
Without gravity,
particles fill
3-D volume
QE
mg
electrode
electrode
Equipotential
contours, from a
plasma simulation
With gravity,
particles
sediment to highfield region
 2-D layer
Compressional Pulse Propagation
We applied a pulse of Argon laser light:
• 0.5 sec duration
• ~2 Watts
• laser beam shaped into a sheet that
intercepts the lattice at 10° angle
• the radiation pressure applies a localized
force to the particles
• measure particle velocity, as difference in
particle position between frames
Sinusoidal Wave Propagation
We modulated the laser power sinusoidally:
• Frequency w is known
• Assume v ~ cos (kx - w t),
(x = distance from laser-excitation region)
• Fourier analyze the particle velocity
• Yields kr and ki
Who cares about dusty plasmas?
Solar system
• Rings of Saturn
• Comet tails
• Planetary formation
Manufacturing
• Particle contamination
(Si wafer processing)
• Nanomaterial synthesis
Basic physics
• Coulomb crystals
• Waves
• Much more ...
Fastest growing area in plasma physics
Comparison of
dusty plasma & pure ion plasmas
Similar:
Different - dusty plasma has:
• Like-charged particles
• Gaseous background
• Yukawa potential
• Crystals & liquids
• 2D or 3D suspensions
• Direct imaging
• Laser-manipulation of
particles
• 105  charge
• no inherent rotation
Dusty who?
Other names for “dusty plasmas”:
• Colloidal plasmas
• Complex plasmas
• Fine-particle plasmas
Wave Propagation Depends on Direction
k

Here we present results for  = 0
The First Physical Sciences Experiment on
the International Space Station:
Plasma Crystal Experiment - March 2001
Flight hardware with 1st & 3rd ISS crews
PI Greg Morfill, Max Planck Institute, Garching Germany
participating countries: Germany, Russia, U.S.
Predecessor Microgravity Experiment:
Sounding Rocket Flights
Morfill et al.,
Phys. Rev. Lett. 1999
Laser sheets
for illuminating
particles
Cameras for
imaging
particles
Other microgravity experiments
1996-1998 Sounding rockets
Morfill et al., PRL 1999
2000 - Mir
Russian “High Energy
Density Research Center”