Here are some movies that correspond to some of our papers:
From our wave experiment (Pieper & Goree, Phys. Rev. Lett., 1996)
These videos are 30 frames taken at a rate of 30 frames per second in
the experiment. The black spots are 9.4 micron polymer spheres. A wave
is launched at a fixed frequency by a wire stretched horizontally above
a lower electrode and through a dust cloud. The camera is viewing straight
down. A horizontal laser sheet illuminates a single plane of particles
in the dust cloud. The wire is not visible in this picture; it runs in
the up-down direction in the orientation of this image, near the left
side of the picture. A low frequency sinusoidal voltage is applied to
the wire, and this causes a local sheath around the wire to expand and
contract, pushing on the nearest particles. The data shown here are for
a gas pressure of 100 mTorr, corresponding to Fig. 2 (b) in our paper.
The modes damp, due to drag of the particles on the neutral gas, as they
propagate to the right. The wave obeys the dispersion relation of a damped
dust acoustic wave. This experiment was carried out by John Pieper.
Limitations of these mpeg movies:
- The images you see in the movies here aren't as big as the ones on the original video tape. The spatial resolution is less.
- Because of MPEG compression, rapidly moving particles look a little elongated.
- The wave-like behavior is more obvious in the original tapes, which are what we analyzed to find the dispersion relation.
The paper can be read online by clicking on this link:
J.B. Pieper and J. Goree
Dispersion of Plasma Dust Acoustic Waves in the Strong Coupling Regime
Physical Review Letters Vol. 77, pp. 3137-3140 1996
Here are the mpeg movies:
From our ionization instability experiment
D. Samsonov & J. Goree
Ionization instabilities in a dusty rf plasma with growing particles
submitted to Phys. Rev. E., March 1998
We recorded the optical glow and the laser light scattering (LLS) simultaneously,
using two different video cameras.
- The video was the same as for Fig. 9 in the paper:
- The cameras viewed exactly the same subject area, and were oriented to view horizontally, at a slightly upward oblique angle. You can see the upper electrode at the top of the picture. It looks like an ellipse, due to the oblique viewing angle.
- The laser sheet for LLS was horizontal.
- The four videos below are about 10 seconds long each.
- Note the flickering of the filamentary mode, and the rotation of the great void mode.
- Limitations of these mpeg videos:
- In order to make the mpeg file size reasonably small, the video quality you will see is not nearly as good as the original video tape.
- The images are cropped, showing only the inter-electrode region. You don't see much of the bottom electrode, and you don't see the dust cloud's full extent in the radial direction, beyond the edge of the electrodes.
- The temporal resolution is reduced by half, since video was digitized at 15 frames per second, dropping every other frame from the 30 fps original.
- The spatial resolution is much lower than the original, due to video compression.
- The two videotapes (glow and LLS) were recorded with common timecodes. Working in our lab in Iowa (USA), we used this timecode to select still images for the paper so that the glow and the LLS pictures are shown at exactly the same time. The MPEG movies shown here, however, were prepared in a lab in Germany, where we did not have access to an NTSC timecode reader, so the glow and LLS videos shown here do not start at precisely the same video frame. They start at approximately the same time, with an accuracy of ~ 2 sec.
Here are the mpeg movies:
From our laser-excited Mach cone experiment
A. Melzer, S. Nunomura, D. Samsonov, Z.W. Ma, and J. Goree
Laser-excited Mach cones in a dusty plasma crystal
Physical Review E Vol. 62, pp. 4162-4176 2000.
A video from a top-view camera. An argon laser beam sweeps over a crystal,
and the optical force from the laser excites Mach cones.
- Laser-excited Mach cone, Mach Number = 1.29
.
