A few images from our older experiments
and simulations appear below. This page is not updated frequently.
Additional older images are in our powerpoint
J. B. Pieper, J. Goree and R.A. Quinn
Three-dimensional structure in a Crystallized Dusty Plasma
Physical Review E Vol. 54, pp. 5636-5640 1996
3D view of a bcc (body-center cubic) crystal formed by 9- micron diameter
plastic microspheres levitated in a krypton radio-frequency discharge.
This image was made by imageing a horizontal sheet of laser light with
a video camera looking down. This was repeated for various heights of
the laser sheet, so that we could assemble a stack of horizontal images.
These are interpolated using Spyglass dicer software, allowing us to present
planar slices that we chose to be aligned with the natural crystal planes.
Only a small part of the cloud is shown here. The green spots are the
particles. We believe this image is the first direct image of the 3D structure
in a crystallized dusty plasma. It appeared on the cover of Bulletin of
The American Physical Society in 1995. This is Fig. 1(a) of the paper
by Pieper, Quinn & Goree 1996
G. Praburam and J. Goree
Cosmic Dust Synthesis by Accretion and Coagulation
Astrophysical Journal Vol. 441, pp. 830-838, 1995
It used to be thought that having a sufficiently clean room would prevent
contamination of large dust particles in the manufacturing of silicon
wafers (and other plasma manufactured devices). Here you can see dust
actually agglomerates in the plasma to large sizes (from nanometers to
10s to even 100s of microns!) In this image you see a carbon electrode
(the background) covered with dust (the white dots). This dust was grown
in the plasma. Once the plasma is turned off, the dust falls onto the
bottom plate which is removed and taken to an electron microscope. (0.7
Below are some higher magnification pictures showing the growth paterns
and varieties of dust.
(0.5 Meg Image)
Here and in the next picture you can see exactly how the dust agglomerates,
forming a coagulated structure. Maybe particles coagulated like this as
the first step in forming planets out of interstellar dust, as has been
hypothesized for the pre-solar nebula that was the precursor to our present
solar system. (0.5 Meg Image)
(0.5 Meg Image
G. Praburam and J. Goree
Evolution of a Particulate Cloud in an RF Plasma
IEEE Transactions on Plasma Science Vol. 24, pp. 97-98, 1996
- Here is a sequence of pictures showing how the dust cloud evolved
in the same experiments that resulted in the carbon grains shown above.
Times are shown in (min:sec). The full 2 cm-high inter-electrode region
is shown. The images are produced by a video camera looking at 90 degrees
at particles illuminated by a sheet of argon laser light. The particles
here are so small that you can't see them individually. This image is
reprinted from our paper in IEEE Trans. Plasma Sci., Special Issue on
Images in Plasma Science, 1996.
Here are more images from the same experiment, this time in black &
white with two contour lines added to aid the eye in identifying features
at low intensity. This is Figure 2 from our paper in Physics of Plasmas,
This is Figure 4 from our paper in Physics of Plasmas, 1996. It shows
the rotation of the "Great Void mode"
This is Figure 5 from our paper in Physics of Plasmas, 1996. It shows
the "Filamentary Mode," which has a vortex-like shape on the left side
of the picture and some wispy structure in the center of the cloud.
This figure shows the experimental setup used for the above figures
from Physics of Plasmas, 1996
Now we have a simulation.
F. MelandsØ and J. Goree
Polarized Supersonic Plasma Flow Simulation for Charged Bodies such
as Dust Particles and Spacecraft
Physical Review E Vol. 52, pp. 5312-5326, 1995
Frank Melandsoe of Tromsoe Norway visited here at The Univ. of Iowa Iowa
for a year, and he wrote a self-consistent 2-fluid simulation of the supersonic
flow of ions past a negatively-charged dust grain. In the upper panels you
see ion density, and in the lower panels electric potential (with the sign
reversed). The ion flow here is downward, from the top, at a spoeed just
slightly faster than the ion acoustic speed. This is from our paper in Physical
Review E, Nov. 1995. Note the ion focus region in the wake downstream of
the circular dust grain; the electric potential there is positive (negative
in these inverted plots) so that a negatively charged grain would be attracted
there. This explains the simple-hexagonal structure that we see in some
of our crystal experiments.
Here is more from the same simulation, this time with two particles aligned
in the vertical direction.