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A few images from our older experiments and simulations appear below. This page is not updated frequently.

Additional older images are in our powerpoint talks.


From

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

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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


From

G. Praburam and J. Goree
Cosmic Dust Synthesis by Accretion and Coagulation
Astrophysical Journal Vol. 441, pp. 830-838, 1995

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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 Meg Image)

Below are some higher magnification pictures showing the growth paterns and varieties of dust.
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(0.5 Meg Image)

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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)

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(0.5 Meg Image


From

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.
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    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, 1996.
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    This is Figure 4 from our paper in Physics of Plasmas, 1996. It shows the rotation of the "Great Void mode"
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    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.
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    This figure shows the experimental setup used for the above figures from Physics of Plasmas, 1996
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From

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

Now we have a simulation.

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.

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